This re-implement "normalization" of the compose model as a plain yaml tree (map[string]any) not relying on compose-go structs conversion. This will make it possible to run the full compose processing (i.e docker compose config) without using go bindings, and then restore support for --no-interpolate and such

note: I dropped support for service.dockerfile and service.log_driver as those were defined by compose file v1 format, and using those should be rejected by schema validation

Also introduce LoadModel in addition to the existing LoadProject so compose-go can be used to partially process a compose file, as illustrated with the included command line:

$ compose-spec --format json --no-interpolation --no-normalization compose.yaml  
{
  "services": {
    "test": {
      "command": "env | grep DEBUG",
      "environment": [
        "DEBUG=${FOO}"
      ],
      "image": "alpine",
      "ports": [
        "${PORT}:80"
      ],
      "x-test": "test"
    }
  }
}