Include SSH client version in access logs

When a client connects to Bitbucket Server via HTTP, the user agent is included in the access logs. However, when a client connects via SSH, the client version is not logged.

As an example of where this would be useful, recent versions of TortoiseGit have upgraded to Plink 0.68, which can cause OutOfMemoryErrors in Bitbucket Server (see BSERV-10100). However, since the client version is not included in the access logs it can be difficult to track such clients down, especially for a busy server with many clients.