Support ssh agent restrictions

[bagajjal]

OpenSSH 8.9 will include the ability to control how and where keys in ssh-agent may be used, both locally and when forwarded (subject to some limitations)

https://www.openssh.com/agent-restrict.html

[bagajjal]

Win32-OpenSSHV8.9 will not support this functionality. This issue is to track adding this support.