Propagate partition tag data to apexkeys.txt and
apkcerts.txt so that merge_target_files.py can build
merged versions of these files by filtering the
framework files for framework partitions and filtering
the vendor files for vendor partitions.
Bug: 138942268
Change-Id: Ic3226728e97dae84d38ec230ccc86d1b124bea94
Bug: 131437873
Test: Built system-only and vendor builds for merge. Compared
resulting apkcertx and apexkeys text files to that of a monolithic
build,
Test: Created colliding entries in both apexkeys and apkcerts text
files and ensure the script exited with an appropriate error message.
Test: Created unit tests to cover both non-colliding and colliding
entries
Change-Id: I6e42ce682ffa9059344e8cd63ba3a720c1f93452