ui/input: change Queue to return Events one at a time

By returning all events, widgets that might return early from its
event loop might throw away subsequent events. Instead of requiring
those widgets to store the event list, convert input.Queue to step
through the available events one at a time.

Functional revert of 1735d5ced8.

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

ui/text/editor.go

@@ -113,7 +113,7 @@ func (e *Editor) Next(cfg ui.Config, queue input.Queue) (EditorEvent, bool) {
 	if (sdist > 0 && soff >= smax) || (sdist < 0 && soff <= smin) {
 		e.scroller.Stop()
 	}
-	for _, ke := range queue.Events(e) {
+	for ke, ok := queue.Next(e); ok; ke, ok = queue.Next(e) {
 		e.blinkStart = cfg.Now()
 		switch ke := ke.(type) {
 		case key.FocusEvent: