Gatekeeperd maintenance

* Move gatekeeper aidl definition to system/core/gatekeeperd
  * Retire hand written IGateKeeperService and use generated instead
  * Adjust gatekeeperd to use the generated aidl stubs.
  * Annotated enroll parameters with @nullable to match the
    documentation and the way it was used. (The hand written
    code was tolerant to null parameters, but it was undefined behavior.)
* Removed Software implementation from gatekeeperd.
  * Also removed the upgrade path.
  * Software implementation including test moved to
    hardware/interfaces/gatekeeper/1.0/software

Change-Id: I72b734db6f67b79b29c2629764490d75d179908a
Merged-In: I72b734db6f67b79b29c2629764490d75d179908a
Test: Manually tested setting pin and login.
13 files changed