Fix SpatialPanel View measure and layout cycle.

For SpatialPanels we manually measure the associated View but we never
call layout. This causes the internal mechanisms for ComposeViews to
never properly finish their layout cycle and report back that the View
was properly laid out (the layout still happens but its "pendingLayout"
state is never updated in some conditions). This was causing
instrumented tests to hang in certain conditions and environments
(emulator).

Bug: 549783316
Test: tested in https://android-review.git.corp.google.com/c/platform/frameworks/support/+/4224199
Change-Id: I313fdeb85bf6445bac23400160370ec2d24da28d