Add tests for TransportStats and some refactor

Added units for http://ag/3709565. Some refactoring.

Test: m -j RunFrameworksServicesRoboTests
Bug: 72485465
Change-Id: Id75a4e0b96936580fd677041e091340b0fff8c1e
(cherry picked from commit cac3a7405997ab9783b537128107a71e6f5b75a2)
2 files changed