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
Major operations:
* Fix the go_package entries to be consistent, as the new tool
complains when it doesn't have a '/'.
* Regenerate with the new protoc-gen-go tool.
* github.com/golang/protobuf -> google.golang.org/protobuf
* proto.[Un]MarshalText -> prototext.[Un]Marshal
Change-Id: Ie1147bd2457fafb66ba555461b3bf14f0561a25d