feat: add fprint support

[TitouanReal]

Adds basic fingerprint support:

I would like to finish this work and allow users to add and remove fingerprints. To continue, I would like official designs to follow.

Technical info useful for design:

• There can be multiple fprint readers.
• It is possible for zero or one of the readers to be marked as "Default".
• Adding a fprint requires its name (right-thumb, left-ring-finger, ...)

For more info, see the doc.

[TitouanReal]

I have seen you put DBus bindinds in here. I believe you would prefer to have a fprint crate in there and use the crate in cosmic-settings.

[mmstick]

Needs input from @maria-komarova then