* make time picker accessible
* use new CustomPaint a11y API
* flutter_localizations tests; use bigger distance delta
* fix am/pm control; selected values
* fix translations; remove @mustCallSuper in describeSemanticsConfiguration
* exclude AM/PM announcement from iOS as on iOS the label is read back automatically
* alwaysUse24HourFormat in MediaQuery and time picker
* docs; dead code
* address some comments
* MaterialLocalizations.timeOfDayFormat is the single source of 24-hour-formattedness
* Make TimePickerDialog private again
* wire up MediaQueryData.fromWindow to Window