GRPC experimental module

[olegbespalov]

What?

This PR brings the experimental GRPC module to a k6.

How to try?

Build a k6

go build .

Run an example service.

go run -mod=mod examples/grpc_server/*.go

and

./k6 run examples/experimental/grpc/server_streaming.js

or

./k6 run examples/experimental/grpc/client_streaming.js

Why?

Related: #2020

[codebien]

👏

[mstoykov]

LGTM just if we can fix the one dependancy

[codecov-commenter]

Codecov Report

Merging #3107 (9e272c1) into master (23ff170) will increase coverage by 0.02%.
The diff coverage is 100.00%.

❗ Current head 9e272c1 differs from pull request most recent head 9d58823. Consider uploading reports for the commit 9d58823 to get more accurate results

@@            Coverage Diff             @@
##           master    #3107      +/-   ##
==========================================
+ Coverage   73.72%   73.74%   +0.02%     
==========================================
  Files         241      241              
  Lines       18461    18457       -4     
==========================================
+ Hits        13610    13612       +2     
+ Misses       3978     3972       -6     
  Partials      873      873              

Flag	Coverage Δ
ubuntu	73.74% <100.00%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
js/jsmodules.go	100.00% <100.00%> (ø)
output/cloud/expv2/output.go	84.14% <100.00%> (+3.68%)	⬆️

... and 1 file with indirect coverage changes