AfwTestHarness needs to use framework-protos from host-side. This is why
new rule is added to build framework-protos usable from host-side.
Change-Id: Ifa35c5de04483d41e97c5853ea781fc29cef4947
First of several change lists:
1. Add in the new proto (this CL)
2. Migrate the existing code over to the proto.
3. Remove MetricsConstants once it is unused.
Bug: 26442178
Change-Id: Ic24829246af8ec5b202e39a85960aac5cf336c33