WIP Start Go RequestResponseIO implementation

[damondouglas]

This PR addresses #28934, addresses #28711, and addresses #28710 using the Go SDK:

• Execute method that wraps a ParDo2 of a caller DoFn
• Integration tests that detect code errors using a Kubernetes deployed gRPC/HTTP endpoint (See https://github.com/apache/beam/tree/master/.test-infra/mock-apis#integration)
• Unit test cover detecting various known API errors within emitted failure PCollection

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[damondouglas]

@riteshghorse and @lostluck FYI

[codecov]

Codecov Report

Attention: 126 lines in your changes are missing coverage. Please review.

Comparison is base (23b1fe9) 37.85% compared to head (6fc9768) 37.80%.
Report is 4 commits behind head on master.

Files	Patch %	Lines
sdks/go/pkg/beam/io/rrio/rrio.go	3.07%	126 Missing ⚠️

Additional details and impacted files

@@            Coverage Diff             @@
##           master   #29488      +/-   ##
==========================================
- Coverage   37.85%   37.80%   -0.06%     
==========================================
  Files         690      691       +1     
  Lines      101307   101476     +169     
==========================================
+ Hits        38353    38360       +7     
- Misses      61362    61520     +158     
- Partials     1592     1596       +4     

Flag	Coverage Δ
go	53.20% <3.07%> (-0.23%)	⬇️

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[damondouglas]

Closing this and will re-submit later when there is time.