Add Support of fido based algorithms in sshd ( OpenSSH Server)

Discussed in https://github.com/PowerShell/Win32-OpenSSH/discussions/2236

^{Originally posted by forrest96 June 2, 2024}
Could you add support for FIDO-backed public key authentication in the OpenSSH Server (sshd)?
This includes the following algorithms:

• sk-ssh-ed25519-cert-v01@openssh.com
• sk-ecdsa-sha2-nistp256-cert-v01@openssh.com
• sk-ssh-ed25519@openssh.com
• sk-ecdsa-sha2-nistp256@openssh.com

The implementation should be straightforward.

Please add the following configurations to sshd_config to indicate the supported implementations:

• PubkeyAuthOptions

• PubkeyAcceptedAlgorithms
  ssh-ed25519-cert-v01@openssh.com,
  ecdsa-sha2-nistp256-cert-v01@openssh.com,
  ecdsa-sha2-nistp384-cert-v01@openssh.com,
  ecdsa-sha2-nistp521-cert-v01@openssh.com,
  sk-ssh-ed25519-cert-v01@openssh.com,
  sk-ecdsa-sha2-nistp256-cert-v01@openssh.com,
  rsa-sha2-512-cert-v01@openssh.com,
  rsa-sha2-256-cert-v01@openssh.com,
  ssh-ed25519,
  ecdsa-sha2-nistp256,ecdsa-sha2-nistp384,ecdsa-sha2-nistp521,
  sk-ssh-ed25519@openssh.com,
  sk-ecdsa-sha2-nistp256@openssh.com,
  rsa-sha2-512,rsa-sha2-256

The issue names no files or tests. Start by locating sshd's public-key authentication and sshd_config handling for PubkeyAuthOptions and PubkeyAcceptedAlgorithms, then trace how the listed FIDO algorithms are recognized. Done means the requested algorithms and configuration options are supported by the Windows OpenSSH server and covered by appropriate existing authentication or configuration checks.