SystemUI: Add flag for IntrinsicLockDispatcher

- This change introduces a feature flag to enable the new
  CoroutineDispatcher for SystemUI that does not make use of
  ReentrantLocks

Flag: com.android.systemui.sysui_intrinsic_lock_dispatcher
Test: N/A - new flag
Bug: 419472502
Change-Id: Ib6f40cfff2f2e464f41f019a0e0eb0b35b2e03e7