docs(input, searchbar, textarea): improve docs for managing focus (#28614)

Issue number: Related to #18132 

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->
The documentation about the `autofocus` prop is unclear and does not
accurately reflect how it actually works across browsers and devices.

## What is the new behavior?
<!-- Please describe the behavior or changes that are being added by
this PR. -->

- The documentation for `autofocus` and `setFocus` are more detailed.
- The documentation links to the relevant page in the docs.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

core/src/components.d.ts

@@ -1162,7 +1162,7 @@ export namespace Components {
          */
         "autocorrect": 'on' | 'off';
         /**
-          * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+          * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.  This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "autofocus": boolean;
         /**
@@ -1274,7 +1274,7 @@ export namespace Components {
          */
         "required": boolean;
         /**
-          * Sets focus on the native `input` in `ion-input`. Use this method instead of the global `input.focus()`.  Developers who wish to focus an input when a page enters should call `setFocus()` in the `ionViewDidEnter()` lifecycle method.  Developers who wish to focus an input when an overlay is presented should call `setFocus` after `didPresent` has resolved.
+          * Sets focus on the native `input` in `ion-input`. Use this method instead of the global `input.focus()`.  Developers who wish to focus an input when a page enters should call `setFocus()` in the `ionViewDidEnter()` lifecycle method.  Developers who wish to focus an input when an overlay is presented should call `setFocus` after `didPresent` has resolved.  See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "setFocus": () => Promise<void>;
         /**
@@ -2601,7 +2601,7 @@ export namespace Components {
          */
         "searchIcon"?: string;
         /**
-          * Sets focus on the native `input` in `ion-searchbar`. Use this method instead of the global `input.focus()`.  Developers who wish to focus an input when a page enters should call `setFocus()` in the `ionViewDidEnter()` lifecycle method.  Developers who wish to focus an input when an overlay is presented should call `setFocus` after `didPresent` has resolved.
+          * Sets focus on the native `input` in `ion-searchbar`. Use this method instead of the global `input.focus()`.  Developers who wish to focus an input when a page enters should call `setFocus()` in the `ionViewDidEnter()` lifecycle method.  Developers who wish to focus an input when an overlay is presented should call `setFocus` after `didPresent` has resolved.  See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "setFocus": () => Promise<void>;
         /**
@@ -2950,7 +2950,7 @@ export namespace Components {
          */
         "autocapitalize": string;
         /**
-          * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+          * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.  This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "autofocus": boolean;
         /**
@@ -3050,7 +3050,7 @@ export namespace Components {
          */
         "rows"?: number;
         /**
-          * Sets focus on the native `textarea` in `ion-textarea`. Use this method instead of the global `textarea.focus()`.
+          * Sets focus on the native `textarea` in `ion-textarea`. Use this method instead of the global `textarea.focus()`.  See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "setFocus": () => Promise<void>;
         /**
@@ -5854,7 +5854,7 @@ declare namespace LocalJSX {
          */
         "autocorrect"?: 'on' | 'off';
         /**
-          * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+          * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.  This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "autofocus"?: boolean;
         /**
@@ -7699,7 +7699,7 @@ declare namespace LocalJSX {
          */
         "autocapitalize"?: string;
         /**
-          * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+          * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.  This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
          */
         "autofocus"?: boolean;
         /**

core/src/components/input/input.tsx

@@ -95,7 +95,9 @@ export class Input implements ComponentInterface {
   @Prop() autocorrect: 'on' | 'off' = 'off';
 
   /**
-   * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+   * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.
+   *
+   * This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
    */
   @Prop() autofocus = false;
 
@@ -424,6 +426,8 @@ export class Input implements ComponentInterface {
    *
    * Developers who wish to focus an input when an overlay is presented
    * should call `setFocus` after `didPresent` has resolved.
+   *
+   * See [managing focus](/docs/developing/managing-focus) for more information.
    */
   @Method()
   async setFocus() {

core/src/components/searchbar/searchbar.tsx

@@ -257,6 +257,8 @@ export class Searchbar implements ComponentInterface {
    *
    * Developers who wish to focus an input when an overlay is presented
    * should call `setFocus` after `didPresent` has resolved.
+   *
+   * See [managing focus](/docs/developing/managing-focus) for more information.
    */
   @Method()
   async setFocus() {

core/src/components/textarea/textarea.tsx

@@ -93,7 +93,9 @@ export class Textarea implements ComponentInterface {
   @Prop() autocapitalize = 'none';
 
   /**
-   * This Boolean attribute lets you specify that a form control should have input focus when the page loads.
+   * Sets the [`autofocus` attribute](https://developer.mozilla.org/en-US/docs/Web/HTML/Global_attributes/autofocus) on the native input element.
+   *
+   * This may not be sufficient for the element to be focused on page load. See [managing focus](/docs/developing/managing-focus) for more information.
    */
   @Prop() autofocus = false;
 
@@ -372,6 +374,8 @@ export class Textarea implements ComponentInterface {
   /**
    * Sets focus on the native `textarea` in `ion-textarea`. Use this method instead of the global
    * `textarea.focus()`.
+   *
+   * See [managing focus](/docs/developing/managing-focus) for more information.
    */
   @Method()
   async setFocus() {