Clean up warnings and fix improper locking in InputManagerService.

Fix up a bunch of warnings from the IDE and errorprone within
InputManagerService. As part of this, fix a number of sensor-related
methods that were holding the wrong lock when accessing
mSensorEventListeners.

Bug: 217923092
Test: errorprone build
Change-Id: I4befdd6682d03406f05b10697a2cda14ac490931