FP3: media: Allow using different files for GSI and non-GSI

* AOSP now adds support for using customized media XML files via sysprops.
* Add this support to use different files for GSI and non-GSI builds.
* The properties are added to system partition so that they get reset
and fallback to AOSP defaults when GSI is flashed.

Change-Id: I6d51c3ac8a5327d92b54d506a972d358b4c96028
(cherry picked from commit 4c76288ade0010493907b62ab64ccc6d91a89e48)