io/input: [API] execute commands immediately

Change the semantics of commands to execute immediately. In cases where
execution of a command introduces a inconsistency, freeze event routing
and defer the command as well as queued events to the next frame.

Rename Source.Queue to Source.Execute to better fit the new command
semantics.

Signed-off-by: Elias Naur <mail@eliasnaur.com>

widget/enum.go

@@ -51,7 +51,7 @@ func (e *Enum) Update(gtx layout.Context) bool {
 			switch ev.Kind {
 			case gesture.KindPress:
 				if ev.Source == pointer.Mouse {
-					gtx.Queue(key.FocusCmd{Tag: &state.tag})
+					gtx.Execute(key.FocusCmd{Tag: &state.tag})
 				}
 			case gesture.KindClick:
 				if state.key != e.Value {