Run php-composer-validate test for all extensions and skins

Bug: 73444
Change-Id: I6cfbd4dfd29b9a00465ec1a742e57d3abfcf3b0f
Rename test zuul_layout to zuul_project_in_gerrit

That lame test just verify that each projects defined in Zuul is
actually defined in Gerrit.  Will reuse zuul_layout to actually test our
Zuul layout.

Change-Id: I55bbc11d272c0a3908c3d57721e914d7c4e202cd