add env and user to inspect in dockercompat

[Shubhranshu153]

Issue:
Docker Compat Inspect doesn't have Env and User parameter for the process

Description:
This PR adds Env and User for the docker compat inspect

Test:

1. Before adding the Env

   "Config": {
            "Hostname": "8ef7e6dbae24",
            "AttachStdin": false,
            "Labels": {
                "dev.containers.id": "base-alpine",
                "dev.containers.release": "v0.4.10",
}

2. After adding the Env:

    "Config": {
      "Hostname": "08826b4795c7",
      "AttachStdin": false,
      "Env": [
        "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
        "HOSTNAME=08826b4795c7"
      ],
  "Labels": {
        "dev.containers.id": "base-alpine",
        "dev.containers.release": "v0.4.10",

}

---

1. Before adding the User

   "Config": {
            "Hostname": "8ef7e6dbae24",
            "AttachStdin": false,
            "Labels": {
                "dev.containers.id": "base-alpine",
                "dev.containers.release": "v0.4.10",
}

2. After adding the User

 "Config": {
            "Hostname": "5dceef466aa1",
            "User": "test",
            "AttachStdin": false,
            "Env": [
                "PATH=/usr/local/sbin:/usr/local/bin:/usr/sbin:/usr/bin:/sbin:/bin",
                "HOSTNAME=5dceef466aa1"
            ],
            "Labels": {
                "devcontainer.config_file": "/Users/shubhum/Documents/devcontainers/.devcontainer/devcontainer.json",
                "devcontainer.local_folder": "/Users/shubhum/Documents/devcontainers",
                }

[AkihiroSuda]

Thanks

[chews93319]

Should c.Config.Env be initialized as an empty list or should the else condition leave the Env key-value pair, in the case that the conditional criteria fails?

[Shubhranshu153]

empty list as not having the key can lead to errors downstream if they query for env from the unmarshalled json and they dont handle key not being present. And also would represent if container process has no set env variables.