feat(searchbar): update styles to iOS 17 specs (#28728)

Issue number: Internal

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## What is the current behavior?
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The searchbar implementation for Ionic's iOS mode does not align with
the appearance of a native search control in iOS 17.

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

- The spacing between the searchbar and the cancel button has increased
to `12px`.
- The cancel button font size has increased to `17px`. 

|iOS 17|Ionic|Diff|
|----|----|----|

|![searchbar-ios](https://github.com/ionic-team/ionic-framework/assets/13732623/883bdeed-ec42-4a1a-898c-82d9d7aa270f)|![ionic-searchbar](https://github.com/ionic-team/ionic-framework/assets/13732623/93482bea-9fae-4056-a6de-8ca5c9e1640d)|![searchbar-diff](https://github.com/ionic-team/ionic-framework/assets/13732623/6c6a1f99-55ab-43be-94e5-bd2ebcd1b960)|


- Ionic's text and background color is different than iOS, this is
expected. Ionic uses the `$text-color-rgb`, which is compatible with
dark mode appearance. Ionic does not currently have rgb variables for
step colors to closer align to iOS color when requiring opacity.
- iOS reference image is from the Notes app. Ionic reference image is
from `searchbar/test/basic`, with a modified content background color of
`#f2f2f7` to closer align to the Notes app.

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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## Other information

<!-- Any other information that is important to this PR such as
screenshots of how the component looks before and after the change. -->

The additional screenshot diffs that are a part of this PR are valid
changes. When updating the color palette for AA contrast, these
reference images were not updated. We currently use a
[threshold](dc1dd9c395/core/playwright.config.ts (L57))
that determines if a diff exists. The reason that they show up in this
PR is because I manually deleted the reference images and forced new
references. As such the text color changes you see here are actually
from the AA contrast changes.

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Co-authored-by: ionitron <hi@ionicframework.com>

core/src/components/searchbar/searchbar.ios.scss

@@ -91,7 +91,7 @@
 // -----------------------------------------
 
 .searchbar-cancel-button {
-  @include padding(0, 0, 0, 8px);
+  @include padding(0, 0, 0, 12px);
 
   flex-shrink: 0;
 

core/src/components/searchbar/searchbar.ios.vars.scss

@@ -17,7 +17,7 @@ $searchbar-ios-padding-start:                     $searchbar-ios-padding-end !de
 
 /// @prop - Font size of the searchbar cancel button
 // The cancel button on iOS does not scale with Dynamic Type
-$searchbar-ios-cancel-button-font-size:           16px !default;
+$searchbar-ios-cancel-button-font-size:           17px !default;
 
 /// @prop - Color of the searchbar cancel button
 $searchbar-ios-cancel-button-color:               ion-color(primary, base) !default;