gRPC's google wrappers support

[olegbespalov]

What?

This PR brings support of google wrappers to the k6.

Why?

The reported in #3232 k6 previously did not correctly marshal the google wrappers messages.

Checklist

• I have performed a self-review of my code.
• I have added tests for my changes.
• I have run linter locally (make ci-like-lint) and all checks pass.
• I have run tests locally (make tests) and all tests pass.
• I have commented on my code, particularly in hard-to-understand areas.

Related PR(s)/Issue(s)

grafana/xk6-grpc#49

Resolves #3232

Closes #3238

Changelog

bug: adds (fixes) the support of google protobuf wrappers

adds (fixes) the support of google protobuf wrappers

[codecov-commenter]

Codecov Report

Patch coverage: 36.11% and project coverage change: -0.20% ⚠️

Comparison is base (f35380f) 73.16% compared to head (112dd59) 72.97%.

❗ Current head 112dd59 differs from pull request most recent head bed4395. Consider uploading reports for the commit bed4395 to get more accurate results

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #3344      +/-   ##
==========================================
- Coverage   73.16%   72.97%   -0.20%     
==========================================
  Files         258      261       +3     
  Lines       19886    19993     +107     
==========================================
+ Hits        14550    14589      +39     
- Misses       4415     4479      +64     
- Partials      921      925       +4     

Flag	Coverage Δ
ubuntu	72.91% <36.11%> (-0.20%)	⬇️
windows	72.81% <36.11%> (-0.21%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Files Changed	Coverage Δ
...httpmultibin/grpc_wrappers_testing/test_grpc.pb.go	14.08% <14.08%> (ø)
...tils/httpmultibin/grpc_wrappers_testing/service.go	62.50% <62.50%> (ø)
...tils/httpmultibin/grpc_wrappers_testing/test.pb.go	90.00% <90.00%> (ø)
lib/netext/grpcext/conn.go	85.71% <100.00%> (ø)

... and 1 file with indirect coverage changes

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