feat(gnobro): add json log format

[gfanton]

Add JSON log format to Gnobro for server usage using the jsonlog flag

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 60.84%. Comparing base (5503cca) to head (149c6e7).
Report is 3 commits behind head on master.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2812      +/-   ##
==========================================
+ Coverage   60.83%   60.84%   +0.01%     
==========================================
  Files         563      563              
  Lines       75193    75190       -3     
==========================================
+ Hits        45743    45753      +10     
+ Misses      26076    26069       -7     
+ Partials     3374     3368       -6     

Flag	Coverage Δ
contribs/gnodev	60.65% <ø> (-0.82%)	⬇️
contribs/gnofaucet	14.46% <ø> (ø)
gno.land	67.17% <ø> (ø)
gnovm	65.63% <ø> (ø)
misc/genstd	80.54% <ø> (ø)
misc/logos	19.88% <ø> (-0.36%)	⬇️
tm2	62.08% <ø> (+0.19%)	⬆️

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