Refine MediaAnalytics framework

Rework some interfaces to avoid unnecessary sp<> mechanisms;
document which side of caller/callee owns pointers afterwards.
Rework internal attribute representation, add support routines.

Bug: 33547720
Test: Boot, ran subset of CTS media tests
Change-Id: Id0d65bd6a847704dc98d38be9aa5e1ce63c20e1c