refactor(material/expansion): use ID generator

Switches to using the ID generator service to create unique IDs.

Author: crisbeto

src/material/expansion/expansion-panel.ts

@@ -32,6 +32,7 @@ import {
   ANIMATION_MODULE_TYPE,
   inject,
 } from '@angular/core';
+import {_IdGenerator} from '@angular/cdk/a11y';
 import {Subject} from 'rxjs';
 import {filter, startWith, take} from 'rxjs/operators';
 import {MatAccordionBase, MatAccordionTogglePosition, MAT_ACCORDION} from './accordion-base';
@@ -42,9 +43,6 @@ import {MatExpansionPanelContent} from './expansion-panel-content';
 /** MatExpansionPanel's states. */
 export type MatExpansionPanelState = 'expanded' | 'collapsed';
 
-/** Counter for generating unique element ids. */
-let uniqueId = 0;
-
 /**
  * Object that can be used to override the default options
  * for all of the expansion panels in a module.
@@ -145,7 +143,7 @@ export class MatExpansionPanel
   _portal: TemplatePortal;
 
   /** ID for the associated header element. Used for a11y labelling. */
-  _headerId = `mat-expansion-panel-header-${uniqueId++}`;
+  _headerId: string = inject(_IdGenerator).getId('mat-expansion-panel-header-');
 
   constructor(...args: unknown[]);