fix(overlays): assign incremental id to overlay host (#27278)

Issue number: Internal

---------

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## What is the current behavior?
<!-- Please describe the current behavior that you are modifying. -->

The counter for incrementing the `id` and `z-index` of an overlay is
incremented whenever the `connectedCallback` is fired for an overlay.

When an overlay is presented and/or conditionally rendered, the overlay
`id` can increment by `n+2` instead of `n+1`.

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

- Increments all overlay ids consistently
- Removes legacy `ion-modal-{id}` and `ion-popover-{id}` logic
- Adds unit tests for the id behavior
- Tests are split up into separate files so that the counter is always
starting from `0`
- Adds an integration test with the Angular test app to verify
conditional rendering behavior

## 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. -->

angular/test/base/src/app/modal-inline/modal-inline.component.html

@@ -17,4 +17,4 @@
       </ion-list>
     </ion-content>
   </ng-template>
-</ion-modal>
+</ion-modal>

angular/test/base/src/app/modal-inline/modal-inline.component.ts

@@ -24,4 +24,5 @@ export class ModalInlineComponent implements AfterViewInit {
   onBreakpointDidChange() {
     this.breakpointDidChangeCounter++;
   }
+
 }