WearMediaOutputSwitcher: Metrics for SASS OutputSwitcher integration

As part of OutputSwitcher and SASS integration we are adding new metrics
for data collection.

Metrics PDD: https://eldar.corp.google.com/assessments/953333269/drafts/456836311/sections/999009000
BUG: 303357497
Test: m

Change-Id: I5184c3b19d51c680f8e62b543ad763e7c7a70a12