Restore focus after node-destroying actions

FormatAction does, and HistoryAction can, destroy nodes so we
need to explicitly restore the selection by focussing the document.

List/IndentationAction only wraps/unwraps content nodes, never
destroying them.

Bug: 57552
Change-Id: I0affff897342f4c3903ac7fc15b015d52b65f8ef
Merge "Restore focus after node-destroying actions"