[BUG] Ambiguous parsing of commands

[AlexRuiz7]

Describe the bug
I found a bug where the action is incorrectly parsed using the generic parser. This happens on commands where action.args is specified before than action.name, as action.name has not been parsed yet and the current logic in unable to determine the action type.

    public static Action parse(XContentParser parser) throws IOException, IllegalArgumentException {
        String name = "";
        Args args = new Args();
        String version = null;

        while (parser.nextToken() != XContentParser.Token.END_OBJECT) {
            String fieldName = parser.currentName();
            parser.nextToken();
            switch (fieldName) {
                case NAME:
                    name = parser.text();
                    break;
                case Args.ARGS:
                    switch (name) {
                        case "set-group":
                            log.info("Parsing arguments for [set-group] command");
                            args = SetGroupCommand.parse(parser);
                            break;
                        case "fetch-config":
                            log.info("Parsing arguments for [fetch-config] command");
                            args = FetchConfigCommand.parse(parser);
                            break;
                        default:
                            log.info("Parsing arguments for [generic] command");
                            args = Args.parse(parser);
                            break;
                    }
                    break;
                case VERSION:
                    version = parser.text();
                    break;
                default:
                    parser.skipChildren();
                    break;
            }
        }

        return new Action(name, args, version);
    }

To Reproduce
Steps to reproduce the behavior:

🟢 Parsed as set-group, as action.name is read first.

{
  "commands": [
    {
      "action": {
        "name": "set-group",
        "args": {
          "groups": [
            "group_1",
            "group_2"
          ]
        },
        "version": "5.0.0"
      },
      "source": "Users/Services",
      "user": "Management API",
      "timeout": 100,
      "target": {
        "id": "d5b250c4-dfa1-4d94-827f-9f99210dbe6c",
        "type": "agent"
      }
    }
  ]
}

🔴 Parsed as generic, as action.args is read first.

{
  "commands": [
    {
      "action": {
        "args": {
          "groups": [
            "group_1",
            "group_2"
          ]
        },
        "name": "set-group",
        "version": "5.0.0"
      },
      "source": "Users/Services",
      "user": "Management API",
      "timeout": 100,
      "target": {
        "id": "d5b250c4-dfa1-4d94-827f-9f99210dbe6c",
        "type": "agent"
      }
    }
  ]
}

Expected behavior
Commands are parsed using the correct parsed independently of the order of the JSON data.

Plugins
Command Manager.

Additional context
Originally posted by @AlexRuiz7 in #253 (review)

[AlexRuiz7]

We probably will need to refactor the parsing of commands to receive not only the parser but the request object, which allows better handling of the content and the creation of several copies of the parser.

request.content()

        /// Request parsing
        /// ===============
        /// Retrieves and generates an array list of commands.
        XContentParser parser = request.contentParser();
        List<Command> commands = new ArrayList<>();
        ensureExpectedToken(XContentParser.Token.START_OBJECT, parser.nextToken(), parser);
        // The array of commands is inside the "commands" JSON object.
        // This line moves the parser pointer to this object.
        parser.nextToken();
        if (parser.nextToken() == XContentParser.Token.START_ARRAY) {
            commands = Command.parseToArray(parser);
        } else {
            log.error("Token does not match {}", parser.currentToken());
        }