Update all expando widgets to use devsite's expandable.

Some other minor cleanup to the markup.

Example staged:
http://go/irina-stage/reference/android/widget/FrameLayout

bug: 72496598
bug: 62903270

test: make ds-docs
Change-Id: Iae1a8e46d67ca25d71de0f7850ffe7a217e68b43
(cherry picked from commit 1660f2a81db1530f7c3d5a35fc1f37587004cf83)
3 files changed