Added more properties associated with user management:

- CREATE_USER: called after an Android user is created.
- REMOVE_USER: called after an Android user is removed.
- USER_IDENTIFICATION_ASSOCIATION: associates an Android user with
  vehicle artifacts like a key FOB.

This CL only defines the new types, they're not implemented or used yet.

Test: m -j android.hardware.automotive.vehicle@2.0-service
Bug: 146207078

Change-Id: Idb399df55567402edb1b954b1c4b25f69e810a81