Build tests against core library impls, not stubs

The libcore tests need access to implementation details
so must be explicitly set to use impl jars before we switch to
stubs by default.

There are some dependencies coming along that have hostdex variants.
These appear to be needed to avoid breaking checkbuild so are also
being added here.

Bug: 113148576
Test: build
Change-Id: Ide3f26976f55ab833375f67dbb20674877815874