[Go SDK]: Implement standalone single-precision float encoder

[jrmccluskey]

Implements a specific single-precision float coder to match Java and Python coder implementations, replacing old routing that treated float32 values as float64 for encoding/decoding purposes.

Fixes #22629

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[codecov]

Codecov Report

Merging #22664 (b51dacb) into master (8fb4945) will increase coverage by 0.00%.
The diff coverage is 76.92%.

@@           Coverage Diff           @@
##           master   #22664   +/-   ##
=======================================
  Coverage   74.19%   74.19%           
=======================================
  Files         708      709    +1     
  Lines       93465    93489   +24     
=======================================
+ Hits        69347    69365   +18     
- Misses      22843    22847    +4     
- Partials     1275     1277    +2     

Flag	Coverage Δ
go	51.54% <76.92%> (+0.02%)	⬆️

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

Impacted Files	Coverage Δ
sdks/go/pkg/beam/core/graph/coder/row_decoder.go	63.82% <70.00%> (+0.09%)	⬆️
sdks/go/pkg/beam/core/graph/coder/float.go	72.72% <72.72%> (ø)
sdks/go/pkg/beam/core/graph/coder/row_encoder.go	68.06% <100.00%> (+0.54%)	⬆️

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[jrmccluskey]

R: @lostluck @TheNeuralBit

[github-actions]

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

[lostluck]

LGTM

I recommend also adding a mention of this to Changes.md, in particular in the breaking changes section, as most coder changes are "breaking", and that this is user observable behavior in the coding.