test(many): replace ionic buttons in e2e tests with native html buttons (#29422)

Issue number: internal

---------

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## What is the current behavior?
The `ion-button` component is used in several tests to navigate or show
overlays. This causes screenshot diffs in unrelated tests any time the
UI of the `ion-button` is updated.

## What is the new behavior?
Removes the `ion-button` elements from unrelated tests. 

Did not remove the `ion-button`s from the following tests:
- All `ion-button`s in an `ion-buttons` component
- An `ion-button` inside of a menu
- breadcrumbs/test/basic (uses a clear button in a list header, needs to
be moved)
- input/test/slot
- item/test/buttons
- item/test/colors
- item/test/dividers
- item/test/inputs
- item/test/media
- list-header/test/basic
- ripple-effect/test/basic
- router/test/basic
- router/test/guards
- router-outlet/test/basic
- select/test/slot
- textarea/test/slot

Updates the icon/basic test to use the right icon names by comparing
against the v3 names: https://ionicframework.com/docs/v3/ionicons/

## Does this introduce a breaking change?

- [ ] Yes
- [x] No

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

core/src/components/picker/test/basic/index.html

@@ -15,6 +15,7 @@
         grid-row-gap: 20px;
         grid-column-gap: 20px;
       }
+
       h2 {
         font-size: 12px;
         font-weight: normal;
@@ -74,7 +75,7 @@
           </div>
           <div class="grid-item">
             <h2>Popover</h2>
-            <ion-button id="popover">Open Picker</ion-button>
+            <button id="popover">Open Picker</button>
             <ion-popover trigger="popover">
               <ion-picker>
                 <ion-picker-column id="popover-first"></ion-picker-column>
@@ -84,7 +85,7 @@
           </div>
           <div class="grid-item">
             <h2>Modal</h2>
-            <ion-button id="modal">Open Modal</ion-button>
+            <button id="modal">Open Modal</button>
             <ion-modal trigger="modal">
               <ion-header>
                 <ion-toolbar>