update config.pb file to the source of truth:
google3/third_party/java_src/android_appbundle/bundletool/schemas/proto/config.proto
current config.pb is stale and needs update.
Also, add a python library host soong module config_proto, so that it
can be used by other python code.
BUG: b/240288941
TETS: tested along with primary_train_build_worker that reuse
BundleConfig.pb
Change-Id: I426a5cb7ec42573ed2110494c50813abc0a96296
dd5beebf4b