Precompute clock view max size, and provide to sysui for layout

Some lockscreen layout decisions (like smartspace date/weather to the
right of the small clock) will be better served by knowing the maximum
size the clock could be at any time, than it's current size since that
can change depending on the current time. This provides that so that
we can make those decisions consistently for a given clock.

Bug: 428993607
Test: Manually checked clock layout
Flag: com.android.systemui.shared.clock_reactive_variants
Change-Id: I9a49425db6a2db689b8c9dff91367113c2860108