Respect config generated by `config-ssh`

I am not sure how feasible this is, but it seems more doable now that `config-ssh` uses wildcards. We generate a separate config because we want to add flags and options. Maybe we could read the SSH config and add anything we are missing? Would need to respect `CODER_SSH_CONFIG_FILE` as well.

Or, can we do something with includes? Or if we use a prefix like `coder.vscode.*` then it will just naturally inherit options.