Support minimum PIN length

[robin-nitrokey]

See § 7.4. Set Minimum PIN Length:

• authenticatorConfig: support setMinPINLength subcommand
• implement minPinLength extension
• set minPinLength option
• adapt authenticatorClientPIN subcommands:
  • setPIN
  • getPinToken
  • changePIN
  • getPinUvAuthTokenUsingPinWithPermissions

Transferred from Nitrokey#84.