Add Logical Display Mapper.

Move the LogicalDisplay creation and management code out of
DisplayManagerService and into LogicalDisplayMapper.  DMS stops
listening to DisplayDevice events directly and now only reacts to
events from LogicalDisplayMapper.

Test: atest frameworks/base/services/tests/servicestests/src/com/android/server/display
Bug: 130724654
Change-Id: I8c8bf94ce0ab85d27f3bbe51f67a1ff75315e09b