Implement SurfaceFragment.rewrapAllNodes

rewrapAllNodes is effectively the same as unwrap then wrap
except it operates as one transaction as so avoids a potentially
invalid intermediate state.

Added some more comments for unwrapAllNodes and renamed a varaible
for consistency.

Fixed a typo in Transaction.newFromWrap comment.

Bug: 45242
Change-Id: Ie752a788d087055d97c7c6f75f59c6a2680d26c7
Merge "Implement SurfaceFragment.rewrapAllNodes"