Pass RPC errorCode to prometheus metrics

[kirugan]

[codecov[bot]]

Codecov Report

Attention: Patch coverage is 50.00000% with 4 lines in your changes missing coverage. Please review.

Project coverage is 78.29%. Comparing base (dc46ab3) to head (43a8f1c). Report is 18 commits behind head on main.

Files	Patch %	Lines
node/metrics.go	50.00%	4 Missing :warning:

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1756      +/-   ##
==========================================
+ Coverage   78.11%   78.29%   +0.17%     
==========================================
  Files         101      101              
  Lines        9062     9057       -5     
==========================================
+ Hits         7079     7091      +12     
+ Misses       1348     1335      -13     
+ Partials      635      631       -4     

:umbrella: View full report in Codecov by Sentry.
:loudspeaker: Have feedback on the report? Share it here.

[kirugan]

Right now we have following RPC errors:

InvalidJSON    = -32700 // Invalid JSON was received by the server.
InvalidRequest = -32600 // The JSON sent is not a valid Request object.
MethodNotFound = -32601 // The method does not exist / is not available.
InvalidParams  = -32602 // Invalid method parameter(s).
InternalError  = -32603 // Internal JSON-RPC error.

In which only InternalError is the most usual one, right now it's not clear how can we distinguish between different error causes for same internal error. So I'm closing the PR for now.