Introduce Message.USER_LOCAL and added logic to map person to user id

1. Introduce Message.USER_LOCAL to allow caller to specify which
   message is from the local user.

2. TextClassifierImpl will now encode the Person object to a user
   id.

3. Fixed a bug in Person.equals check

BUG: 111437455
BUG: 111406942

Test: atest frameworks/base/core/tests/coretests/src/android/view/textclassifier/ActionsSuggestionsHelperTest.java

Change-Id: I6629f42244a402fa210f87afa88a629c2ca4a510