Add HWC2::setBlockingRegion

Implement from here down: the blocking region is passed to
HidlComposerHal (which ignores it) and AidlComposerHal (which respects
it).

Depends on Ib0fa41e56196feeff201637d5599830d2565da2b.

Bug: 212736475
Test: TODO (b/213361853)
Change-Id: I991c8e1beca22075ec831f96dff218e6af3d9a08