`nsIEditor.undo` and `nsIEditor.redo` are called with `1` except by the search
bar, and search bar wants to undo everything to reset the value. Therefore,
search bar needs an API to undo all, and the others do not need the number of
undoing/redoing transactions. Therefore, this patch adds `nsIEditor.undoAll`
for search bar, and remove the arguments from `nsIEditor.undo` and
`nsIEditor.redo`.
Differential Revision: https://phabricator.services.mozilla.com/D158338
89ceba2ffb