Introduce SuggestionSpan#getLocaleObject().

This is a series of CLs to promote Java Locale object as a primary data
object to represent locale information in Android APIs.

With this CL, developers can get Locale information from SuggestionSpan
without semantically losing the original data.  Possible use cases would
be:
 - Emoji subtag (CLDR Ticket #9063)
 - Stable and reliable 3-letter country codes handling
 - Custom attributes based on private extensions.

Note that this CL does not change the current behavior of
SuggestionSpan#getLocale() as is, even if it is created with a malformed
Locale object:

  new SuggestionSpan(new Locale(" a ", " b c ", " e"), new String[0], 0)
          .getLocale() -> " a  b c  e".

Bug: 22858221
Change-Id: I96dfd4f819a236ee2e6dbd3e12903d1214223cb0