feat(ngMock): invoke nested calls to `module()` immediately

Before 1.3, it was possible to call `angular.mock.module()` from inside
another module. After this version additional calls were just ignored.

It is helpful to be able to do this since a test may have helper functions
that need to access "config"-time things such as constants or providers,
and without this change it is difficult to get hold of the `$provide`
object from within those helpers.

Closes #12887