Generalize ART APEX flavor handling in `art_apex_test.py`.

Introduce flag `--flavor` in `build/apex/art_apex_test.py` to select
the flavor of the ART APEX to check (`release`, `debug`, `testing`,
`auto`). Default to `auto`, which auto-detects the flavor based on the
name of the APEX passed as argument to the script.

Update `build/apex/runtests.sh` and `build/apex/Android.bp` to use
these new options instead of `--debug` and `--testing`.

Test: art/build/apex/runtests.sh
Bug: 139277987
Change-Id: I463ae6504576f77ee70b3ac4111bd43c49e450d0
3 files changed