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

<!-- If this introduces a breaking change, please describe the impact
and migration path for existing applications below. -->


## Other information

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screenshots of how the component looks before and after the change. -->

core/src/components/loading/loading.tsx

@@ -14,6 +14,7 @@ import {
   present,
   createDelegateController,
   createTriggerController,
+  setOverlayId,
 } from '../../utils/overlays';
 import type { OverlayEventDetail } from '../../utils/overlays-interface';
 import type { IonicSafeString } from '../../utils/sanitization';
@@ -212,6 +213,7 @@ export class Loading implements ComponentInterface, OverlayInterface {
       const mode = getIonMode(this);
       this.spinner = config.get('loadingSpinner', config.get('spinner', mode === 'ios' ? 'lines' : 'crescent'));
     }
+    setOverlayId(this.el);
   }
 
   componentDidLoad() {

core/src/components/loading/test/loading-id.spec.ts

@@ -0,0 +1,41 @@
+import { newSpecPage } from '@stencil/core/testing';
+
+import { Loading } from '../loading';
+
+it('loading should be assigned an incrementing id', async () => {
+  const page = await newSpecPage({
+    components: [Loading],
+    html: `<ion-loading is-open="true"></ion-loading>`,
+  });
+  let loading: HTMLIonLoadingElement;
+
+  loading = page.body.querySelector('ion-loading')!;
+
+  expect(loading).not.toBe(null);
+  expect(loading.getAttribute('id')).toBe('ion-overlay-1');
+
+  // Remove the loading from the DOM
+  loading.remove();
+  await page.waitForChanges();
+
+  // Create a new loading to verify the id is incremented
+  loading = document.createElement('ion-loading');
+  loading.isOpen = true;
+  page.body.appendChild(loading);
+  await page.waitForChanges();
+
+  loading = page.body.querySelector('ion-loading')!;
+
+  expect(loading.getAttribute('id')).toBe('ion-overlay-2');
+
+  // Presenting the same loading again should reuse the existing id
+
+  loading.isOpen = false;
+  await page.waitForChanges();
+  loading.isOpen = true;
+  await page.waitForChanges();
+
+  loading = page.body.querySelector('ion-loading')!;
+
+  expect(loading.getAttribute('id')).toBe('ion-overlay-2');
+});

core/src/components/loading/test/loading.spec.ts

@@ -1,15 +1,16 @@
 import { newSpecPage } from '@stencil/core/testing';
-import { Loading } from '../loading';
-import { config } from '../../../global/config';
 
-describe('alert: custom html', () => {
+import { config } from '../../../global/config';
+import { Loading } from '../loading';
+
+describe('loading: custom html', () => {
   it('should not allow for custom html by default', async () => {
     const page = await newSpecPage({
       components: [Loading],
       html: `<ion-loading message="<button class='custom-html'>Custom Text</button>"></ion-loading>`,
     });
 
-    const content = page.body.querySelector('.loading-content');
+    const content = page.body.querySelector('.loading-content')!;
     expect(content.textContent).toContain('Custom Text');
     expect(content.querySelector('button.custom-html')).toBe(null);
   });
@@ -21,7 +22,7 @@ describe('alert: custom html', () => {
       html: `<ion-loading message="<button class='custom-html'>Custom Text</button>"></ion-loading>`,
     });
 
-    const content = page.body.querySelector('.loading-content');
+    const content = page.body.querySelector('.loading-content')!;
     expect(content.textContent).toContain('Custom Text');
     expect(content.querySelector('button.custom-html')).not.toBe(null);
   });
@@ -33,7 +34,7 @@ describe('alert: custom html', () => {
       html: `<ion-loading message="<button class='custom-html'>Custom Text</button>"></ion-loading>`,
     });
 
-    const content = page.body.querySelector('.loading-content');
+    const content = page.body.querySelector('.loading-content')!;
     expect(content.textContent).toContain('Custom Text');
     expect(content.querySelector('button.custom-html')).toBe(null);
   });