This CL builds NetworkStats related code with the
connectivity module instead of platform.
This includes:
1. Add netstats.proto to the module.
2. Add lib dependencies for all callers.
3. Include several source files in platform and add jarjar rule
to it. Modify callers accordingly.
Test: TH
Bug: 197717846
Change-Id: I244693aebe1782d9e67502638ff8145c51462e1e
a8f1f762eb