ComposeClock: Add basic structure for the compose clock

Create a generic compose clock with its view model and composable. Right
now, it only shows the current time and does not respond to anything.
Future CLs will add more functionalities for the clock on top of this
basic structure.

Also adds some small updates to the current clock interactor.

Bug: 390204943
Flag: com.android.systemui.clock_modernization
Test: ClockViewModelTest
Change-Id: I35d1e3be4e3e9a2503eedf3b354579a6643b447e