* 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

...and document what I did.

* introduce localized text geometry in MaterialLocalizations

* remove geometry from color text themes

* fix merge conflict

* optional Localizations

* fix fallback; test; docs

* misc .arb fixes; localizations validator

* regenerate localizations

* address comments

* do not treat plural variations as invalid keys

* Internationalize the time picker

- header layout and formatting
- 12-hour vs 24-hour dial
- RTL

* make TimeOfDayFormat an enum

* address comments