Move calls to SafetyCenterManager to bg

Move the calls to `handleInitialize` in the tile so they are called in
the bg thread. This method is always called before tiles are ready, so
it should not change behavior.

Test: manual, long press goes to correct activity
Test: atest CameraToggleTileTest MicrophoneToggleTileTest
Fixes: 407698587
Flag: EXEMPT bug fix

Change-Id: Id12c19e2e9729704c42267151b9a554eecdb2d68