Merge changes from topics "async-challenge", "lss-sp"

* changes:
  Remove remainder of generateChallengeBlocking
  BiometricEnrollIntro should use non-blocking generateChallenge
  4/n: Remove challenge from choose/confirm, use new path
  3/n: verifyCredential no longer returns RequestThrottledException
  2/n: Add setRequestGatekeeperPassword to ChooseLockSettingsHelper