Apex: support codenames for min_sdk_version

Apex can use codenames like "Q", "R" for its min_sdk_version property.
Also, cc_library can use codenames for its stubs.versions.

Bug: 152655956
Test: vendor/google/build/build_mainline_modules.sh
Change-Id: I077ad7b2ac5d90b4c8708921e43846206f05ba70