4/n: Remove challenge from choose/confirm, use new path

Biometric enrollment will not request a Gatekeeper HAT during
initial credential setup or credential confirmation anymore.
Instead, it is broken down into the following steps now.

Bug: 161765592

1) Request credential setup / confirmation to return a
   Gatekeeper Password
2) Biometric enrollment will generate a challenge
3) Biometric enrollment will request LockSettingsService to
   verify(GatekeeperPassword, challenge), and upon verification,
   the Gatekeeper HAT will be returned.

Since both LockSettingsService and Biometric enroll/settings
make use of biometric challenges, this allows us to make the
challenge ownership/lifecycle clear (vs. previously, where
LockSettingsService has no idea who the challenge belongs to).

Exempt-From-Owner-Approval:For files not owned by our team,
(StorageWizard), this change is just a method rename

Test: RunSettingsRoboTests

Run the following on face/fingerprint devices
Test: Remove credential
      adb shell am start -a android.app.action.SET_NEW_PASSWORD
      Set up credential + fingerprint
Test: Remove credential,
      adb shell am start -a android.settings.FINGERPRINT_SETTINGS
      This tests the ChooseLock* logic in FingerprintSettings
Test: Set up credential,
      adb shell am start -a android.settings.FINGERPRINT_SETTINGS
      This tests the ConfirmLock* logic in FingerprintSettings
Test: Remove device credential, enroll fingerprint/face. Succeeds.
      This tests the ChooseLock* returning SP path from
      BiometricEnrollIntro
Test: With credential and fingerprint/face enrolled, go to
      fingerprint/face settings and enroll. This tests the
      ConfirmLock* path in Fingerprint/FaceSettings
Test: Remove device credential, enroll credential-only, enroll
      fingerprint/face separately. Succeeds. This tests the
      ConfirmLock* returning SP path in BiometricEnrollIntro
Test: In SUW, set up credential, then biometric. This tests
      the ChooseLock* path in SUW
Test: In SUW, set up credential, go back, then set up biometric.
      This tests the ConfirmLock* path in SUW

Change-Id: Idf6fcb43f7497323d089eb9c37125294e7a7f5dc