Separate Nitrokey FIDO2 and generic FIDO2 commands

[robin-nitrokey]

Some fido2 commands work with any FIDO2 device, some only with the Nitrokey FIDO2. We have received multiple reports that this is confusing, for example:

• nk3 fido2 status  #453
• warn user before running nitropy fido2 update on nitrokey 3 devices? #536
• nkpk fido2 verify results in unknown fingerprint #594

We should clearly indicate which commands only work for the Nitrokey FIDO2 and potentially move them to a separate command:

• check VID/PID in Nitrokey FIDO2 commands
  • fido2: Limit VID/PID for Nitrokey FIDO2 commands #604
• review help messages
• to be discussed: introduce a separate command for Nitrokey FIDO2 device, e. g. nkfido2 or nk-fido2
  • move subcommands to the new command
  • add aliases for the old commands showing a deprecation warning