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/scripts/testing/styles.css

@@ -48,3 +48,23 @@ html.ios.ios {
   --ion-font-family: -apple-system, BlinkMacSystemFont, "iosTestingFont", sans-serif;
   font-family: -apple-system, BlinkMacSystemFont, "iosTestingFont", sans-serif;
 }
+
+ion-content button,
+main button {
+  display: inline-block;
+  width: auto;
+  clear: both;
+  padding: 12px 8px;
+  font-size: 1em;
+  background: #008080;
+  border: 1px solid #005555;
+  color: #fff;
+  border-radius: 4px;
+  margin: 8px 0;
+}
+
+ion-content button.expand,
+main button.expand {
+  display: block;
+  width: 100%;
+}