[#24339] Make Slices use iterable coder instead of custom coder.

[lostluck]

Changes the default encoding of Go slices to use the beam iterable coder format.

Technically this is the same format as before, but without a length prefix.

Changing coder implementations are generally a breaking change, however this only applies to streaming updates or when trying to re-use the internal pipeline coders. The benefit of cross language compatibility longer term, in a format expected by go users, is perceived to be a larger benefit.

Fixes #24339.

Additionally:

• Changes to make exec structure debugging more consistent and useful.

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[codecov]

Codecov Report

Merging #24346 (e380bbf) into master (d2211bd) will increase coverage by 0.01%.
The diff coverage is 70.37%.

❗ Current head e380bbf differs from pull request most recent head 13404d2. Consider uploading reports for the commit 13404d2 to get more accurate results

@@            Coverage Diff             @@
##           master   #24346      +/-   ##
==========================================
+ Coverage   73.34%   73.36%   +0.01%     
==========================================
  Files         718      718              
  Lines       96966    97034      +68     
==========================================
+ Hits        71120    71187      +67     
+ Misses      24515    24503      -12     
- Partials     1331     1344      +13     

Flag	Coverage Δ
go	51.55% <70.37%> (+0.10%)	⬆️

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

Impacted Files	Coverage Δ
sdks/go/pkg/beam/core/runtime/exec/datasource.go	62.00% <0.00%> (ø)
sdks/go/pkg/beam/core/runtime/graphx/dataflow.go	51.71% <50.00%> (-2.23%)	⬇️
sdks/go/pkg/beam/core/typex/fulltype.go	48.82% <54.54%> (+7.32%)	⬆️
sdks/go/pkg/beam/coder.go	56.33% <64.28%> (+1.38%)	⬆️
sdks/go/pkg/beam/core/runtime/graphx/coder.go	52.23% <80.00%> (+0.32%)	⬆️
sdks/go/pkg/beam/core/runtime/exec/translate.go	17.46% <85.71%> (+4.73%)	⬆️
sdks/go/pkg/beam/core/runtime/exec/pardo.go	59.60% <100.00%> (ø)
... and 1 more

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[lostluck]

Run Go PostCommit

[lostluck]

R: @riteshghorse

This should unblock RunInference.

[github-actions]

Stopping reviewer notifications for this pull request: review requested by someone other than the bot, ceding control

[lostluck]

Looks like not having a comprehensive test runner for all the different versions and variants of what runners can do strikes again! Should be simple enough though.

Specifically, Dataflow appears to turn something into the "state backed" coder, and I'm missing the appropriate handling for it in some instances.

[lostluck]

Run Go PostCommit

[lostluck]

Run Go Flink ValidatesRunner

[lostluck]

Run Go Flink ValidatesRunner

[lostluck]

Run Go PostCommit

[riteshghorse]

minor nits but LGTM. Thanks for unblocking!

[lostluck]

Thanks for the review!