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/back-button/test/host-element/index.html

@@ -28,7 +28,7 @@
             <ion-content class="ion-padding">
               <h1>Page One</h1>
               <ion-nav-link router-direction="forward" component="page-two">
-                <ion-button class="next">Go to Page Two</ion-button>
+                <button>Go to Page Two</button>
               </ion-nav-link>
             </ion-content>
         `;
@@ -51,7 +51,7 @@
               <h1>Page Two</h1>
               <div>
                 <ion-nav-link router-direction="forward" component="page-three">
-                  <ion-button class="next">Go to Page Three</ion-button>
+                  <button>Go to Page Three</button>
                 </ion-nav-link>
               </div>
             </ion-content>
@@ -75,7 +75,7 @@
               <h1>Page Three</h1>
               <div>
                 <ion-nav-link router-direction="forward" component="page-four">
-                  <ion-button class="next">Go to Page Four</ion-button>
+                  <button>Go to Page Four</button>
                 </ion-nav-link>
               </div>
             </ion-content>