Using a dedicated thread executor for MSDL haptics

Some interactions have been experiencing delayed hapics (see bug in this
CL) due to haptics firing if a -sometimes- busy background thread. Like
in SysUI, we can avoid this by using a newSingleThreadExector when
firing one-shot MSDL feedback.

Test: manual. Rapidly selected different wallpapers and verified haptics
  played in sync with the UI update.
Flag: com.android.launcher3.msdl_feedback
Bug: 391384092

Change-Id: I1661c85976c4744058e046c7ff8386bb99c6d50b