gralloc: Read debug properties in allocator process

This change resolves selinux denials caused by system processes
reading vendor debug properties via gralloc. The debug properties
are read and parsed in the allocator process, then propagated
through the BufferManager.

CRs-Fixed: 2619084
Change-Id: I5175a7848cdcd2671bd16ee11721066a921f3d79
10 files changed