Integrate connectionServiceFocusManager into call flow

This changed allows multiple calls existed at the same time by
mataining the ConnectionService focus.

design doc: go/android-telecom-3p-enhancements
Bug: 69651192
Test: unit test

Change-Id: I57777daec2011df958d0483ad0876cff55ee0133
Merged-In: I57777daec2011df958d0483ad0876cff55ee0133