gcsio.py use RuntimeError with exc chaining instead of overwriting previous exception

[cozos]

gcsio.py use RuntimeError with exc chaining instead of overwriting previous exception

addresses #26769 (comment)

cc: @tvalentyn

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[codecov]

Codecov Report

Merging #28470 (3f21506) into master (5df59a9) will decrease coverage by 0.01%.
The diff coverage is 0.00%.

@@            Coverage Diff             @@
##           master   #28470      +/-   ##
==========================================
- Coverage   72.34%   72.33%   -0.01%     
==========================================
  Files         683      683              
  Lines      100709   100709              
==========================================
- Hits        72855    72852       -3     
- Misses      26274    26277       +3     
  Partials     1580     1580              

Flag	Coverage Δ
python	82.83% <0.00%> (-0.01%)	⬇️

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Files Changed	Coverage Δ
sdks/python/apache_beam/io/gcp/gcsio.py	88.60% <0.00%> (ø)

... and 5 files with indirect coverage changes

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[jrmccluskey]

LGTM