[spidermate][code executor] add csharp support

Summary:
Added C# support, based off the AWS service: https://fburl.com/ngnfc9f3 - using mcs (instead of csc that the AWS service is using) for compilation, and mono for execution.

Note, the image wouldn't build due to mono-core breaking rpm scripts. Added bypass and follow-up task T206575712.

Test Plan:
# UTs

Added UTs:
```
[stolerman@devvm32682.lla0 ~/fbsource/fbcode/spidermate/code_executor (csharp)]$ buck test code_handler:test_code_handlers
```
https://www.internalfb.com/intern/testinfra/testrun/14918173821638790

# tested on local server

Built and ran vaagent with the updated image:
```
[stolerman@devvm32682.lla0 ~/fbsource/fbcode (csharp)]$ buck2 run mode/opt //crackerjack/vaagent/:run_vaagent -- spidermate_execution_env --image //crackerjack/vaagent/image/execution_env/:rootfs.ext3
```

Pointed the service to the local vaagent in the vmaas engine:
```
        client = create_vaagent_client(
            # ip=None,
            # port=None,
            # tiername=VMAAS_TIER,
            # NOTE: comment out the above 3 lines and uncomment the below lines to run locally
            # (see https://www.internalfb.com/intern/wiki/Spidermate/Code_Executor/#add-dependencies-to-the)
            ip="127.0.0.1",
            port=9001,
            tiername=None,
        )
```

Ran the service:
```
[stolerman@devvm32682.lla0 ~/fbsource/fbcode/spidermate/code_executor (csharp)]$ TW_PORT_thrift=54127 buck run mode/opt //spidermate/code_executor:service
```

Ran tests on thrift fiddle:

## (1) simple hello world

**Endpoint:** `devvm32682.lla0.facebook.com:54127`
**Method:** `executeCode`

**Request Body**

```lang=json
{
    "execute_code_request": {
        "code": {
            "code_snippet": {
                "snippet": "using System;\n\nnamespace HelloWorld\n{\n  class Program\n  {\n    static void Main(string[] args)\n    {\n      Console.WriteLine(\"hello world!\");\n    }\n  }\n}\n",
                "language": "CSHARP",
            }
        }
    }
}
```

**Request Headers**

```lang=json
{"client_id":"test"}
```

**Response Body**

```lang=json
{
    "process_output": {
        "exitCode": 0,
        "stdout": [
            "hello world!"
        ],
        "stderr": []
    }
}
```

[Load request in Thrift Fiddle](https://fburl.com/thrift_fiddle/2ov2ozm2)

## (2) using refs

Ran another test using `System.Numerics` from the provided references:

**Endpoint:** `devvm32682.lla0.facebook.com:54127`
**Method:** `executeCode`

**Request Body**

```lang=json
{
    "execute_code_request": {
        "code": {
            "code_snippet": {
                "snippet": "using System;\nusing System.Numerics;\n\nnamespace HelloWorld\n{\n  class Program\n  {\n    static void Main(string[] args)\n    {\n      Vector2 a = new Vector2(1f, 1f);\n      Vector2 b = new Vector2(2f, 2f);\n      Console.WriteLine(a + b);\n    }\n  }\n}\n",
                "language": "CSHARP",
            }
        }
    }
}
```

**Request Headers**

```lang=json
{"client_id":"test"}
```

**Response Body**

```lang=json
{
    "process_output": {
        "exitCode": 0,
        "stdout": [
            "<3, 3>"
        ],
        "stderr": []
    }
}
```

[Load request in Thrift Fiddle](https://fburl.com/thrift_fiddle/nuxqx87r)

## (3) specifying main class

**Endpoint:** `devvm32682.lla0.facebook.com:54127`
**Method:** `executeCode`

**Request Body**

```lang=json
{
    "execute_code_request": {
        "code": {
            "code_snippet": {
                "snippet": "using System;\n\nnamespace HelloWorld\n{\n  class Program\n  {\n    static void Main(string[] args)\n    {\n      Console.WriteLine(\"hello world!\");\n    }\n  }\n}\n",
                "language": "CSHARP",
                "properties": {"CSHARP__CLASS": "HelloWorld.Program"},
            }
        }
    }
}
```

**Request Headers**

```lang=json
{"client_id":"test"}
```

**Response Body**

```lang=json
{
    "process_output": {
        "exitCode": 0,
        "stdout": [
            "hello world!"
        ],
        "stderr": []
    }
}
```

[Load request in Thrift Fiddle](https://fburl.com/thrift_fiddle/fhdmwtf9)

## (4) specifying wrong main class

**Endpoint:** `devvm32682.lla0.facebook.com:54127`
**Method:** `executeCode`

**Request Body**

```lang=json
{
    "execute_code_request": {
        "code": {
            "code_snippet": {
                "snippet": "using System;\n\nnamespace HelloWorld\n{\n  class Program\n  {\n    static void Main(string[] args)\n    {\n      Console.WriteLine(\"hello world!\");\n    }\n  }\n}\n",
                "language": "CSHARP",
                "properties": {"CSHARP__CLASS": "HelloWorld.IDontExist"},
            }
        }
    }
}
```

**Request Headers**

```lang=json
{"client_id":"test"}
```

**Response Body**

```lang=json
{
    "process_output": {
        "exitCode": 1,
        "stdout": [
            "Compilation failed: 1 error(s), 0 warnings"
        ],
        "stderr": [
            "error CS1555: Could not find `HelloWorld.IDontExist' specified for Main method"
        ]
    }
}
```

[Load request in Thrift Fiddle](https://fburl.com/thrift_fiddle/hvjcfyox)

Reviewed By: azarian

Differential Revision: D65397190

fbshipit-source-id: 2d78e44e1621eaec3884c23f9973201c0ed1e33d

antlir/antlir2/features/rpm/driver.py

@@ -101,6 +101,7 @@ def package_struct(pkg):
     "git-lfs": "TODO(T170621965)",
     "nsight-compute-2019.4.0": "TODO(T166170831)",
     "coreutils-common": "TODO(T182347179)",
+    "mono-core": "TODO(T206575712)",
 }