Provide a new config option "perl.ttyCmd" to allow the language server to be run in Docker containers, Kubernetes pods, and other modern solutions

[Nowaker]

Currently, the only way to start a remote language server is using SSH. While this works for truly remote situations, it doesn't fill the bill for modern environments like Docker containers, systemd-nspawn containers, remote containers in Kubernetes clusters, etc. To make this work, we need a way to define a command that provides a TTY for the extension to run its commands. For example, for Docker, it would be something like docker exec -it [containername] bash. For Kubernetes, kubectl exec -it [podname] bash. For systemd-nspawn, machinectl shell [machinename]. The effect is the same as executing the SSH - acquisition of TTY where commands can be executed. But it's not SSH per say.

We need a new configuration options, e.g. perl.ttyCmd that is responsible of providing a TTY for the plugin.

[Nowaker]

I've managed to hack my way around using sshCmd and stripping some of the parameters passed to it before passing the rest to the container. The example below is for docker-compose but there's nothing prevent you from tuning it to do docker exec, kubectl exec, machinectl shell or whatnot.

.vscode/settings.json

{
  "perl": {
    "enable": true,
    "sshAddr": "dummy",
    "sshUser": "dummy",
    "sshCmd": "bin/shell-into-appserver.sh",
    "sshWorkspaceRoot": "/home/code (directory in the container)",
    "logLevel": 0,
  }
}

bin/shell-into-appserver.sh:

#!/usr/bin/env bash
COMMAND=$(echo "$@" | sed 's/^.*perl /perl /')
docker-compose exec -u "$UID" -T [SERVICE NAME] $COMMAND

[richterger]

I putted your "ssh" settings example for docker in the README committed in 1bcef8814de898e1bff72397fffc50a158263ae5