Fallback to legacy intent factory when the template is null

When RemoteActionTemplate[] is null, it means the intent generator
is not working, we then fallback to legacy intent factory
If RemoteActionTemplate[] is an empty array, it means the intent
generator is run, but no intent is generated.

Also, moved all intent related class to intent/ folder

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

Change-Id: I7e4c49dc3ebed4d498ac26f0894d7af85419419e