Support SSH Certificate Authentication

Bitbucket should have support to SSH Keys certificate auth.

SSH has a specification that defines support for SSH certificates.
SSH certificates allow one SSH key to sign another SSH key, resulting in an “SSH certificate”. A server that trusts the CA is able to verify the certificate’s signature and trust the certificate and its associated metadata.

After signed server keys are updated by bitbucket admin, users do not need to update their local ssh keystore

For reference https://ibug.io/blog/2019/12/manage-servers-with-ssh-ca/