ComposeClock: Apply custom AM/PM styling to the new clock

Add the support of custom AM/PM styling to the new composable clock. The
old Clock.java support normal, gone, and small style. However, only
normal and gone styles are in use today, so we will only support these 2
types in the new clock.

Future callers of this clock should use the view model to define which
style to use.

Bug: 390204943
Flag: com.android.systemui.clock_modernization
Test: ClockViewModelTest
Change-Id: I41cd8cd5a3c037e31214ed21df30b0366954a0de