Add a feature flag for SPA metrics

- Add a new SETTINGS_ENABLE_SPA_METRICS flag.

Fixes: 277540990
Bug: 253979024
Test: atest SpaActivityTest SpaLogDataTest MetricsDataModelTest
Change-Id: I6da801691fd34fd133ec25d3a45ed6124bec51a1
Merged-In: Iba7a44715cf6ba78c3b84d559faf71a0be33d8d3
1 file changed