Launch settings for clicking fingerprint unlock

Launch FingerprintSettings directly when user clicks "Fingerprint
Unlock". Let Fingerprint settings peform confirmLock() or chooseLock().
And to have smoothly animation, instead of generating challenge in
FingerprintSettings::onActivityResult(), challenge is generated in next
visible activity, and pass it back through next activity result.

Bug: 197717071
Test: atest GatekeeperPasswordProviderTest CredentialModelTest
Test: atest AutoCredentialViewModelTest FingerprintStatusUtilsTest
Test: RunSettingsRoboTests2 FingerprintEnrollIntroductionTest
Test: Manually test fingerprint enroll in settings or suw
Change-Id: Ie27c3c493ea475f6b53cb6bb3f2d45d555f47cb3