Keystore 2.0: Revisit Enforcements.

This patch revisits the Keystore 2.0 enforcements module to support
KM4.1 hardware enforced device locked keys.
* Consolidate the background handler into async_task.
* The auth token handler became AuthInfo and was moved into
  enforcements.rs.
* The auth token validity check moved from database.rs to
  enforcements.rs.

Bug: 171503362
Test: Keystore CTS tests
Change-Id: If37d38183901b356242079af812c7a0e1e79abf3
10 files changed