Add erigon_nodeInfo API implementation

[lupin012]

closes #410

[codecov[bot]]

Codecov Report

Merging #411 (a77ac48) into master (266e3a0) will increase coverage by 0.06%. The diff coverage is 90.19%.

@@            Coverage Diff             @@
##           master     #411      +/-   ##
==========================================
+ Coverage   81.72%   81.78%   +0.06%     
==========================================
  Files         106      106              
  Lines        6943     6994      +51     
  Branches     1396     1401       +5     
==========================================
+ Hits         5674     5720      +46     
- Misses        797      800       +3     
- Partials      472      474       +2     

Impacted Files	Coverage Δ
silkrpc/commands/erigon_api.hpp	100.00% <ø> (ø)
silkrpc/ethbackend/backend.hpp	100.00% <ø> (ø)
silkrpc/json/types.hpp	75.00% <ø> (ø)
silkrpc/commands/erigon_api.cpp	33.21% <69.23%> (+1.67%)	:arrow_up:
silkrpc/ethbackend/remote_backend.cpp	98.79% <95.83%> (-0.24%)	:arrow_down:
silkrpc/json/types.cpp	98.36% <100.00%> (+0.03%)	:arrow_up:

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.