Only undo on MWMetaDialog close if small stack is non-empty

Added return boolean to ve.dm.Surface#breakpoint to indicate if
and transactions were pushed to the big stack. Use this value in
MWMetaDialog to see if we need to undo on close.

Added tests for ve.dm.Surface#breakpoint.

Bug: 49630
Change-Id: Ieb2e9e361afe057af93c4d374acc85df58bfb4c3
Merge "Only undo on MWMetaDialog close if small stack is non-empty"