Rename isSecureLockDeviceAvailable and return type

Renames isSecureLockDeviceAvailable to getSecureLockDeviceAvailability
and renames IntDef return type IsSecureLockDeviceAvailableRequestStatus
to GetSecureLockDeviceAvailabilityRequestStatus.

Flag: android.security.secure_lock_device
Fixes: 420637357
Fixes: 420636407
Test: atest SecureLockDeviceServiceTest
Change-Id: Ibac25b08b1a94d1eea07cb30878745501f622fcd