Add shunts for Beam typehints to apache_beam.dataframe.schemas

[TheNeuralBit]

Currently we only support mapping typing.Optional, we should also support beam.typehints.Optional.

GitHub Actions Tests Status (on master branch)

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[TheNeuralBit]

Extracted from #22575

[codecov]

Codecov Report

Merging #22680 (e1ad20e) into master (c9c57a7) will decrease coverage by 0.00%.
The diff coverage is 100.00%.

@@            Coverage Diff             @@
##           master   #22680      +/-   ##
==========================================
- Coverage   74.19%   74.18%   -0.01%     
==========================================
  Files         708      708              
  Lines       93465    93467       +2     
==========================================
- Hits        69347    69343       -4     
- Misses      22843    22849       +6     
  Partials     1275     1275              

Flag	Coverage Δ
python	83.59% <100.00%> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
sdks/python/apache_beam/dataframe/schemas.py	97.67% <100.00%> (+0.03%)	⬆️
.../python/apache_beam/testing/test_stream_service.py	88.09% <0.00%> (-4.77%)	⬇️
sdks/python/apache_beam/utils/interactive_utils.py	95.12% <0.00%> (-2.44%)	⬇️
.../python/apache_beam/transforms/periodicsequence.py	98.38% <0.00%> (-1.62%)	⬇️
...che_beam/runners/interactive/interactive_runner.py	90.06% <0.00%> (-1.33%)	⬇️
sdks/python/apache_beam/transforms/combiners.py	93.05% <0.00%> (-0.39%)	⬇️
...eam/runners/interactive/interactive_environment.py	91.71% <0.00%> (-0.31%)	⬇️
...hon/apache_beam/runners/worker/bundle_processor.py	93.30% <0.00%> (-0.25%)	⬇️
...ks/python/apache_beam/runners/worker/sdk_worker.py	89.09% <0.00%> (+0.15%)	⬆️
sdks/python/apache_beam/io/gcp/bigquery.py	74.24% <0.00%> (+0.20%)	⬆️
... and 2 more

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R: @yeandy for label python.

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[yeandy]

LGTM