AAPT2: Add flag to print multi APK artifact names.

- Added new flag that exits after printing the list of artifact names
  that would be generated from the combination of the configuration file
  and input APK.

- Cleaned up the code to generate the artifact names which also involved
  adding some more test cases for corner cases.

Test: Unit tests
Test: Manually ran new command
Test: Manually ran old command
Change-Id: I8d30e7a4a070af26945b8f544a13f23bdf1ba169