* Move SubtypeLocale.get{Full,Middle,Short}DisplayName() to
LatinLeyboardView and add unit tests (SpacebarTextTests).
* Add SubtypeLocale.getSubtypeDisplayName()
This is a cherry-pick of I57420c6a from Master.
Bug: 6393865
Change-Id: I68748189c17c73984ac4ae05a5a40fb54bf46453