FingerprintSettings: Add proximity check awareness if supported

Fingerprint authentication when screen is off doesn't nativelly
support checking the proximity sensor status to prevent accidental
unlocks. However, some devices implement this feature, so account
for that. The only thing really needed is just to adapt the
descriptions shown to the users.

Change-Id: I635f7b1a2970c0364b6cd22dfe20e69d009a3f91