When unlocking, show only "fingerprint unlocking" button if "Biometric Unlocking" option is enabled

**Is your feature request related to a problem? Please describe.**

There are 2 unlocking button, one is for "Biometric Unlocking" (on the left) and usual unlocking with passwords (on the right) if "Biometric Unlocking" option is enabled. Showing 2 buttons on the screen is quite error-prone.

**Describe the solution you'd like**

Show just one "Biometric Unlocking" button for the first attempt, and show two buttons after the user canceled the "fingerprint unlocking" attempt, since "Biometric Unlocking" will be the first choice for most users with "Biometric Unlocking" option enabled.

**Describe alternatives you've considered**

There can be an option to choose between the current behavior and the proposed behavior.

Start by locating the Android unlock screen and the biometric-unlocking flow, then trace how the two unlock buttons are shown and how cancellation is handled. Done means that enabling Biometric Unlocking shows only the biometric button initially, while canceling it reveals both buttons.

Written by the indexing model from the issue text.