[ADisplay] Expose preferred WCG format per-display

This mirrors the api exposed by the SDK.

Similarly to the other ADisplay apis, the intention is that these apis
will be #apex stable, but the map file doesn't need to be updated until
HWUI is shipping in an updatable module.

Bug: 144505134
Test: builds
Change-Id: I2a06e4c304edb28d4580ef0aef4431ec8df2d94e