fix: hook up high level metrics

[brianluong]

Description

Hook up high level metrics. They were missing.

Type of change

• 🐛 Bug fix (non-breaking change which fixes an issue)
• 😎 New feature (non-breaking change which adds functionality)
• ⁉️ Breaking change (fix or feature that would cause existing functionality to not work as expected)
• ⚒️ Refactor (no functional changes)
• 📖 Documentation (updating or adding docs)

How Has This Been Tested?

➜  node-gateway git:(main) ✗ 
➜  node-gateway git:(main) ✗ curl localhost:9090 | grep rpc_requests
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 58508    0 58508    0     0  6510k      0 --:--:-- --:--:-- --:--:-- 55.7M
➜  node-gateway git:(main) ✗ curl localhost:8080/eth
404 page not found
➜  node-gateway git:(main) ✗ curl localhost:8080/mainnet
{"message":"Method not allowed."}%                                                                                                                                                    
➜  node-gateway git:(main) ✗ curl localhost:9090 | grep rpc_requests
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 90827    0 90827    0     0  12.3M      0 --:--:-- --:--:-- --:--:-- 86.6M
# HELP node_gateway_server_rpc_requests Count of total RPC requests.
# TYPE node_gateway_server_rpc_requests counter
node_gateway_server_rpc_requests{chain_name="mainnet",code="405",method="get"} 1
➜  node-gateway git:(main) ✗ curl localhost:8080/matic              
{"message":"Method not allowed."}%                                                                                                                                                    
➜  node-gateway git:(main) ✗ curl localhost:9090 | grep rpc_requests
  % Total    % Received % Xferd  Average Speed   Time    Time     Time  Current
                                 Dload  Upload   Total   Spent    Left  Speed
100 93503    0 93503    0     0  9409k      0 --:--:-- --:--:-- --:--:-- 89.1M
# HELP node_gateway_server_rpc_requests Count of total RPC requests.
# TYPE node_gateway_server_rpc_requests counter
node_gateway_server_rpc_requests{chain_name="mainnet",code="405",method="get"} 1
node_gateway_server_rpc_requests{chain_name="matic",code="405",method="get"} 1