[Notification Content Cut Off] use max child height in ConversationLayout

FrameLayout measures its match_parent children twice when any of FLs dimension is unspecified.
It also sets its dimension before the match parent childrens second measurement.
Since View#measure is not immutable, children can have a different dimensions.
When the biggest children has bigger height than its first measurement, its content is going to be cut off.
We calculate the maxHeight in this CL and set it to fix cut off issue.

Bug: 324537506
Flag: android.widget.flags.conversation_layout_use_maximum_child_height
Test: Manual. Disable child invalidation and optimize linearlayout. Post a group notification with short choices and trigger onMeasure twice by orientation change. There shouldn't be any cut off.
Change-Id: I02be31dea83a217247c2e0dff05ceaa88efb2dee