sdm: hwc2: Add support for TWM entry and exit.

- Implement SET_STAND_BY_MODE binder support. SKGHAL
  use this api to inform HWC about TWM entry/exit.
- Move to null display to drop all incoming calls
  from surfaceflinger on TWM entry.
- Move to normal display on TWM exit.
- Add scope_lock for SET_STAND_BY_MODE API.

Bug: 79541227
CRs-Fixed: 2200577
Change-Id: I26ef3b1af53856f68f76b116988cc2a28c06b6ac
8 files changed