Switch i18n listeners to use IME hint locales

Previously, the i18n listeners were keyed off the text locales of the
TextView. This could create some unanticipated backward
compatibility headaches. The IME hint locales seems to be a better
match, since they are supposed to be used for input.

Fixes: 37249649
Fixes: 37133729
Fixes: 37222714
Bug: https://code.google.com/p/android/issues/detail?id=2626
Bug: 8319249
Bug: 33276673
Bug: 34394455
Bug: 37160895
Test: Updated and added CTS tests pass
Change-Id: If8a115f3e30ff1601dee426a504984e2ce24a776