Add test_for property

This change adds 'test_for' property to cc_test_* types. The property is
used to mark a module as a test for one or more APEXes, in which case
the module has accecss to the private part of the listed APEXes. For
example, the module is linked with the actrual shared library in the
APEX instead of the stub of the shared library.

Exempt-From-Owner-Approval: already +2'ed by owner

Bug: 129539670
Bug: 153046163
Test: m
Change-Id: I45ed0d7a15540b0d69b2a3b8d9c4cb202adff6f2