fix(ivy): support ng-container inside another ng-container

[pkozlowski-opensource]

This PR takes care of the following cases wrt to <ng-container>:

Nested <ng-container>:

<ng-container>
  <ng-container>
    <ng-container>
      content
    </ng-container>
  </ng-container>
</ng-container>

Nested <ng-container> in a view with delayed insertion:

<ng-template testDirective>
	<ng-container>
	  <ng-container>
	    <ng-container>
	      content
	    </ng-container>
	  </ng-container>
	</ng-container>
</ng-template> 

Changes in the code are minimal so most of the diff is about tests.

[mary-poppins]

You can preview 8de4940 at https://pr25346-8de4940.ngbuilds.io/.

[JoostK]

In the canInsertNativeNode counterpart, we account for grandParent being null here. Is that relevant here too?

[pkozlowski-opensource]

Nope, since we've already checked (in the canInsertNativeNode) that it can be inserted so there should be a render parent somewhere above.

[mhevery]

http://test/OCL:207736620:BASE:207736655:1533662378110:4476dd8f

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