Merge "Document resources staging groups and finalization" into tm-dev am:...

Merge "Document resources staging groups and finalization" into tm-dev am: 1b4cf0ce am: 522a825a

Original change: https://googleplex-android-review.googlesource.com/c/platform/frameworks/base/+/17076571

Change-Id: I7b65419a792816f82f10ac67f2d344eb54e87a4b