Add a common utility for dev to use to log files

The common utility will ensure that stuff logged is always
in a format that we can read on the infra side.
Provide a JUnit4 Rule to log file from device side in a
similar way as the host-side.

Test: build, run unit tests
Bug: 28218068
Change-Id: Ib2e7cda756cdd8fafb8b1909eedbb31bb97f2485