Fixes two layout issues with lockscreen compose

1. Reduce top padding by the clock. This removes the statusbar height
   added into the padding because the clock is positioned below the
   status bar and that height is already calculated in.
2. Ensure using the global rect top of the notification place holder
   view in NPVC. Instead of using whatever else calculation, we just
   want to use whereever the placeholder is when ComposeLockscreen is
   enabled.

Bug: 301968149
Test: look at small clock
Test: pull down shade in split shade
Flag: ACONFIG com.android.systemui.compose_lockscreen DEVELOPMENT

Change-Id: Ia5f793b14de6203228343ae42b7e6fa341abe66f