textInputFade becomes colorFade in theme.go and serves AvatarGroup,
Image retry, Tag and EditableText, which used internal.Fade. MyGo already
skips element transitions under ReduceMotion, so dropping the Motion
check keeps behaviour.
EditableTextView.Changed is a method like every other result's.
AlertDialogResult, PopconfirmResult and DateTimeResult spell Canceled
the American way, matching EditableTextView and LoadingOverlayResult.
Callers, Gallery and docs updated.
ZacharyZhang-NY