Add a setting to allow a user to choose the native image format

This will allow two things while we wait for a formalized image format
scheme:
(1) We can pass PTS tests that rely on the native format
(2) If exposed, users can set it so the stack will request the high
quality native image format when compatible with Android

Bug: b/150332574
Test: Build, flash, interop with Cover devices, atest
Change-Id: Ia154a97312959b18eaa1c43bdee3bb02912683f2
Merged-In: Ia154a97312959b18eaa1c43bdee3bb02912683f2