test(ivy): add root cause analysis for the remaining projection test (#28152)

Initial thinking was that the bug is in the content projection logic but
it turned out to be a wrong assumption - hence adding a test to illustrate
that basic content projection of view containers works correctly.

What fails in the marked test is the logic quering debug nodes - content
peojection is fine but we never create the 'B' text node since we call
show() method on the "wrong" directive instance.

PR Close #28152

packages/core/test/linker/projection_integration_spec.ts

@@ -543,7 +543,33 @@ describe('projection', () => {
     expect(main.nativeElement).toHaveText('B(A)');
   });
 
-  fixmeIvy('unknown').it('should project filled view containers into a view container', () => {
+  it('should project view containers', () => {
+    TestBed.configureTestingModule(
+        {declarations: [SingleContentTagComponent, ManualViewportDirective]});
+    TestBed.overrideComponent(MainComp, {
+      set: {
+        template: '<single-content-tag>' +
+            '<div class="target">A</div>' +
+            '<ng-template manual class="target">B</ng-template>' +
+            '<div class="target">C</div>' +
+            '</single-content-tag>'
+      }
+    });
+
+    const main = TestBed.createComponent(MainComp);
+    const manualDirective =
+        main.debugElement.queryAllNodes(By.directive(ManualViewportDirective))[0].injector.get(
+            ManualViewportDirective);
+
+    expect(main.nativeElement).toHaveText('AC');
+
+    manualDirective.show();
+    main.detectChanges();
+    expect(main.nativeElement).toHaveText('ABC');
+  });
+
+  fixmeIvy('FW-869: debugElement.queryAllNodes returns nodes in the wrong order')
+      .it('should project filled view containers into a view container', () => {
         TestBed.configureTestingModule(
             {declarations: [ConditionalContentComponent, ManualViewportDirective]});
         TestBed.overrideComponent(MainComp, {