more testable MetricsLogger interface

Begin migration to non-static methods to allow easier mocking.
New clients should use the non-static methods.
Old clients that want to unit test metrics
should move to the new interface.

Bug: 35138327
Test: runtest --path frameworks/base/packages/SystemUI/tests/src/com/android/systemui/statusbar/phone/StatusBarTest.java
Change-Id: I168f3787ee50ddde8aa2d42c05b2b816d1d3a30e