[Co-ex] Show 'too_dark' face acquired messages

Update message. If fingerprint is enrolled, and face too_dark message
is received, then tell the user to there's not enough light (for face
auth) and suggest trying fingerprint to unlock.

Test: atest KeyguardIndicationControllerTest
Fixes: 234886175
Fixes: 243405121
Change-Id: Ia40e0e01895b04b906924d967763bb48d53124b5