gralloc: Add automatic format selection. DO NOT MERGE

Have gralloc_alloc be able to select the appropriate pixel format
given the endpoints, triggered by new
GRALLOC_EMULATOR_PIXEL_FORMAT_AUTO format.

Currently supports camera->screen, and camera->video encoder.

Bug: 6243944
Change-Id: Ib1bf8da8d9184ac99e7f50aad09212c146c32809
3 files changed