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: Ifcf64664f61d1b792daa1cab504d9045f2dbc975
Merged-In: Ifcf64664f61d1b792daa1cab504d9045f2dbc975