logcat: Add --regex option

(cherry pick from commit dc42a8734e5394eef022984de528718e195a0e8e)

You can now filter log output by a regex on the messages.

Test: New unit test passes
Bug: 27706081
Change-Id: Idfa637f62a25fb1b92e9b49b89572dff0fec6e08
3 files changed