fix(ivy): sync ViewRefs between multiple ViewContainerRefs (#30985)

Previously, multiple ViewContainerRef instances (obtained by injecting
ViewContainerRef multiple times) each had private state that could be out of
sync with actual LContainer, if views were inserted/removed/queried across
the different instances. In particular each instance had its own array which
tracked ViewRefs inserted via that instance.

This commit moves the ViewRefs array onto the LContainer itself, so that it
can be shared across multiple ViewContainerRef instances. A test is added
that verifies ViewContainerRefs now provide a consistent view of the
container.

FW-1377 #resolve

PR Close #30985

packages/core/test/acceptance/di_spec.ts

@@ -1202,6 +1202,37 @@ describe('di', () => {
             // Each ViewContainerRef instance should be unique
             expect(otherDirective.isSameInstance).toBe(false);
           });
+
+      it('should sync ViewContainerRef state between all injected instances', () => {
+        @Component({
+          selector: 'root',
+          template: `<ng-template #tmpl>Test</ng-template>`,
+        })
+        class Root {
+          @ViewChild(TemplateRef, {static: true})
+          tmpl !: TemplateRef<any>;
+
+          constructor(public vcr: ViewContainerRef, public vcr2: ViewContainerRef) {}
+
+          ngOnInit(): void { this.vcr.createEmbeddedView(this.tmpl); }
+        }
+
+        TestBed.configureTestingModule({
+          declarations: [Root],
+        });
+
+        const fixture = TestBed.createComponent(Root);
+        fixture.detectChanges();
+        const cmp = fixture.componentInstance;
+
+        expect(cmp.vcr.length).toBe(1);
+        expect(cmp.vcr2.length).toBe(1);
+        expect(cmp.vcr2.get(0)).toEqual(cmp.vcr.get(0));
+
+        cmp.vcr2.remove(0);
+        expect(cmp.vcr.length).toBe(0);
+        expect(cmp.vcr.get(0)).toBeNull();
+      });
     });
 
     describe('ChangeDetectorRef', () => {