Fix outdated code in python sdk install

[Abacn]

A follow up of #23227. Noticed that the error reporting logic was not accurate either.

Fix outdated code in python sdk install

• /sdks/common no longer exists. proto are in /model

• Clean up findSupportedPython.groovy in PYTHON_SDK_ROOT

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[Abacn]

Seems like .pyi files were generated and packaged but .py files were not generated.

[codecov]

Codecov Report

Merging #23231 (3733050) into master (9d9db56) will decrease coverage by 0.00%.
The diff coverage is n/a.

@@            Coverage Diff             @@
##           master   #23231      +/-   ##
==========================================
- Coverage   73.58%   73.58%   -0.01%     
==========================================
  Files         716      716              
  Lines       95316    95327      +11     
==========================================
+ Hits        70140    70148       +8     
- Misses      23880    23883       +3     
  Partials     1296     1296              

Flag	Coverage Δ
python	83.40% <ø> (-0.01%)	⬇️

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

Impacted Files	Coverage Δ
.../apache_beam/runners/interactive/dataproc/types.py	93.10% <0.00%> (-3.45%)	⬇️
.../python/apache_beam/transforms/periodicsequence.py	98.38% <0.00%> (-1.62%)	⬇️
...s/python/apache_beam/io/gcp/bigquery_file_loads.py	87.24% <0.00%> (-0.61%)	⬇️
...hon/apache_beam/runners/worker/bundle_processor.py	93.54% <0.00%> (-0.13%)	⬇️
...che_beam/runners/interactive/interactive_runner.py	91.39% <0.00%> (+1.32%)	⬆️
.../python/apache_beam/testing/test_stream_service.py	92.85% <0.00%> (+4.76%)	⬆️

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[yeandy]

LGTM

[Abacn]

Thanks @yeandy
R: @tvalentyn

[github-actions]

R: @tvalentyn for final approval

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