cmd/protoc-gen-go-grpc: default use_generic_streams_experimental to true

[arvindbr8]

relnotes for cmd/protoc-gen-go-grpc:

• Generated code for services will produce streaming method definitions using one of six different generic types (e.g. BidiStreamingServer or ClientStreamingClient) instead of producing complete interfaces and implementations for the streaming methods. This can be disabled by setting use_generic_streams_experimental=false. Please file a bug if you encounter any issues with this behavior. This will become the default behavior in an upcoming release.

RELEASE NOTES: NONE

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 81.46%. Comparing base (4e9b596) to head (e67a330).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #7387      +/-   ##
==========================================
+ Coverage   81.30%   81.46%   +0.16%     
==========================================
  Files         348      348              
  Lines       26744    26744              
==========================================
+ Hits        21744    21788      +44     
+ Misses       3800     3771      -29     
+ Partials     1200     1185      -15     

see 23 files with indirect coverage changes