Use Dailer.SetKeepAliveConfig on go1.23+

[ignoramous]

Why? golang/go#48622 / tailscale/tailscale#3363

Ref: golang/go#62254

[Lanius-collaris]

I'd like to use syscall first if I can test before v055o (I don't know the release date) 🤗.

[ignoramous]

I'd like to use syscall first

You could, but isn't go1.23 only a week or two away...