Fixes the transformation of metrics.

This changes slightly the way metrics are converted from the HIDL
interface to the MediaDrm interface. This provides a cleaner
representation for querying metrics.

Bug: 73724453
Test: New and existing unit tests. Updated and existing GTS. Google Play
manual.

Change-Id: I9be170784a19ca3e89add53cea1cdfcaad6d65eb