[Notif redesign] Fix top line alignment for larger children

I found this bug while investigating something related, and although it's not currently visible because the children of the top line view are generally always smaller in height, it's still worth fixing since the onLayout actually supports taller children, but this bug breaks that support.

The issue was that although the onLayout implementation correctly aligns children taller than the parent vertically, in the measure phase, we were actually limiting children's height to the given height, which broke the alignment in the end.

Bug: 378660052
Test: visual test, screenshot tests to come later
Flag: android.app.notifications_redesign_templates
Change-Id: I3a03e09b91b220663b7994263b4af5b2d9d07cfc