This patch replaces the usage of the deprecated FingerprintManager API with
BiometricPrompt. This uses the Android X library, so we get the native biometric
prompt on recent versions of Android and a Google-made one on older versions. By
not working with custom prompts for biometric authentication like we do now, we
can be sure that any issues like #70, #81, #237 are not actually our fault.
Here's what it looks like:
As a nice aside, this also adds support for the new facial recognition as an
authentication method on Pixel 4 phones.
This is still a draft, but early feedback is welcome.
