[sb] operator name view model for home status bar

This implements a StatusBarOperatorNameViewModel and Binder which mimic
the old behavior of the operator name view.

Test: HomeStatusBarViewModelImplTest
Test: StatusBarOperatorNameViewModelTest
Test: manual
Bug: 364360986
Flag: com.android.systemui.status_bar_root_modernization
Change-Id: Iee34f1972fe0feef8e35a543fdc3ccf57861ff69