refactor(test): <template>/<ng-container>/*-directives

- remove outer `<div>` in tests,
- use `<ng-container>` instead of `<template>` where possible,
- use *... instead of template (tag or attr) where possible.

Fixes #13816

modules/@angular/core/test/linker/direct_rendering_integration_spec.ts

@@ -138,7 +138,7 @@ export function main() {
       @Component({
         selector: 'child',
         template:
-            '(<template [ngTemplateOutlet]="templateRef" [ngOutletContext]="templateCtx"></template>)'
+            '(<ng-container [ngTemplateOutlet]="templateRef" [ngOutletContext]="templateCtx"></ng-container>)'
       })
       class Child {
         @Input()

modules/@angular/core/test/linker/view_injector_integration_spec.ts

@@ -421,7 +421,7 @@ export function main() {
         TestBed.overrideDirective(
             SimpleDirective, {set: {providers: [{provide: 'service', useValue: 'parentService'}]}});
         const el = createComponent(
-            '<div simpleDirective><template [ngIf]="true"><div *ngIf="true" needsService></div></template></div>');
+            '<div simpleDirective><ng-container *ngIf="true"><div *ngIf="true" needsService></div></ng-container></div>');
         expect(el.children[0].children[0].injector.get(NeedsService).service)
             .toEqual('parentService');
       });