Implement smarter locale resource selection

* Add support for determining script from language and region.
* Add support for determining special parents of locales.
* Add support for smart comparison of locales with only a difference
  in region, using the locale parentage tree.
* Fix LocaleData.matchScore() to not fallback to old locale matching
  behavior if we can't determine a script.
* Allow four-character variant codes. (Previously, only five- to
  eight-character variant codes were allowed.)

Bug: 7296673
Bug: 26589793
Change-Id: Ibde0a48c0564ff383b41068095a5cbacfe7b94bc