Enrich test cases when enabling default IMEs

This is another groundwork for subsequent fixes.

Notable changes in test cases are:
- isAsciiCapable is now annotated accordingly.
- "dummy.keyboard0" now has several subtypes like
  "en_GB", "en_IN", "hi", "hi_ZZ" like the AOSP
  LatinIME.

BUG: 17347871
Change-Id: Ide698ed11c2539ba5862e6b37ea63ed19f8ce566