Fix gRPC log parsing

[t0yv0]

Using "google.golang.org/protobuf/encoding/protojson" instead of vanilla JSON solves the problem of parsing the logs correctly to a gRPC representation.

[codecov]

Codecov Report

Attention: Patch coverage is 78.57143% with 3 lines in your changes are missing coverage. Please review.

Project coverage is 37.99%. Comparing base (3a38438) to head (c62df5f).
Report is 3 commits behind head on main.

Files	Patch %	Lines
grpclog/grpclog.go	78.57%	1 Missing and 2 partials ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##             main      #86      +/-   ##
==========================================
+ Coverage   37.35%   37.99%   +0.64%     
==========================================
  Files          43       46       +3     
  Lines        2677     2779     +102     
==========================================
+ Hits         1000     1056      +56     
- Misses       1569     1607      +38     
- Partials      108      116       +8     

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