Change Logcat to only log in background thread in debug mode

The prod and always log trackers shoud just log syncrhonously, since they
do not do any jank-causing work to determine whether a message should be
logged.
Bug: 221419865
Test: ran 'atest SystemUITests SystemUIGoogleTests'

Change-Id: I2e673a480abbd5afda2d6ce3117df47e0415ea8a