Implement GET v2/node/version endpoint

[chong-he]

Issue Addressed

Partly #9045

Additional Info

Response with only beacon node (EC not shown at all):

{
  "data": {
    "beacon_node": {
      "code": "LH",
      "name": "Lighthouse",
      "version": "v8.1.3",
      "commit": "13dd00ab"
    }
  }
}

Response with both BN and EC:

{
  "data": {
    "beacon_node": {
      "code": "LH",
      "name": "Lighthouse",
      "version": "v8.1.3",
      "commit": "13dd00ab"
    },
    "execution_client": {
      "code": "GE",
      "name": "go-ethereum",
      "version": "1.15.11-stable",
      "commit": "36b2371c"
    }
  }
}

[chong-he]

This is copied from:

lighthouse/beacon_node/execution_layer/src/engine_api/json_structures.rs

Lines 1064 to 1074 in 176cce5

	#[derive(Debug, Clone, Serialize, Deserialize)]
	#[serde(rename_all = "camelCase")]
	pub struct JsonClientVersionV1 {
	pub code: String,
	// This `default` is required until Geth v1.13.x is no longer supported on mainnet.
	// See: https://github.com/ethereum/go-ethereum/pull/29351
	#[serde(default)]
	pub name: String,
	pub version: String,
	pub commit: String,
	}

I wanted to do: use execution_layer::json_structures::JsonClientVersionV1, but adding execution_layer in Cargo.toml under eth2 will create a cyclic dependency issue when compiling. So I ended up just created another one. Probably not ideal, so happy to revise according to the feedback about this

[chong-he]

Not sure if it is ok to hardcode "LH" here? I wanted to do this:

lighthouse/beacon_node/execution_layer/src/engine_api/http.rs

Lines 96 to 102 in 176cce5

	pub static LIGHTHOUSE_JSON_CLIENT_VERSION: LazyLock<JsonClientVersionV1> =
	LazyLock::new(|| JsonClientVersionV1 {
	code: ClientCode::Lighthouse.to_string(),
	name: "Lighthouse".to_string(),
	version: VERSION.replace("Lighthouse/", ""),
	commit: COMMIT_PREFIX.to_string(),
	});

but it involves using ClientCode which is also from the execution_layer, which will also cause cyclic dependency issue