Delay `UIAlertController.onDismiss` #463

Job	Run time
library (15.4, ios)	9m 53s
Windows (windows-latest, debug)	5m 28s
library (15.4, macos)	7m 10s
Windows (windows-latest, release)	14m 15s
library (15.4, tvos)	9m 43s
library (15.4, watchos)	7m 26s
library (15.4, examples)	9m 7s
	1h 3m 2s

Provide feedback