Partially fix#21213.
This PR will get client IP address from SSH_CONNECTION env which should
be the first field of that. And deliver it to the internal API so Gitea
routers could record the real IP from SSH requests.
Co-authored-by: wxiaoguang <wxiaoguang@gmail.com>
Co-authored-by: 6543 <6543@obermui.de>
Co-authored-by: zeripath <art27@cantab.net>