Add callback for when enrollment state changes

Bug: 195663312

(New tests):
Test: manual, FingerprintManager no longer shows up in strict
      mode logs when changing keyguard states
Test: atest FingerprintStateCallbackTest

(Existing cases below):
Test: atest com.android.server.biometrics
Test: atest CtsBiometricsTestCases
Test: atest com.android.systemui.biometrics
Test: atest KeyguardUpdateMonitorTest

Change-Id: I57304f9ed938cbe4ec63683b826ead086cc33a5b