Move !StackContainer/!StackController to use native keydown/keypress events, rather than synthetic dojo/_base/connect::_keypress event.   The onkeypress data-dojo-attach-event's in the templates technically still map to dojo/_base/connect::_keypress, but the code is no longer depending on evt.charOrCode, or for keypress events to fire for non-printables.  Also clearing dangling uses of deprecated this.connect().  Refs #16585 !strict.