[SB][Call] Small re-organization of CallChipViewModel code

This will make it easier to do a separate click listener if promoted
notification chips are enabled.

Bug: 364653005
Flag: EXEMPT refactor
Test: Trigger call chip with ui_rich_ongoing both on and off -> verify
it works as expected
Test: atest CallChipViewModelTest

Change-Id: I71f9dc6267ab3c64c546fc8eba7fd4c70eda9314