[BEAM-13250] Factorise gcsio.GcsIO() from gcsfilesystem

[mlhamel]

Here is a proposition of change to fix https://issues.apache.org/jira/browse/BEAM-13250

Basically I wanted to make the demonstration of an easy of factorizing gcsio.GcsIO() from gcsfilesytem to make it easier to create some kind of replacement for it to inject custom parameters like a custom url for th gcs server.

R: @aaltay @charlesccychen

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[codecov]

Codecov Report

Merging #15977 (01c6ea9) into master (fd00fc9) will decrease coverage by 0.04%.
The diff coverage is 84.61%.

@@            Coverage Diff             @@
##           master   #15977      +/-   ##
==========================================
- Coverage   83.65%   83.60%   -0.05%     
==========================================
  Files         445      445              
  Lines       61362    61365       +3     
==========================================
- Hits        51331    51306      -25     
- Misses      10031    10059      +28     

Impacted Files	Coverage Δ
sdks/python/apache_beam/io/gcp/gcsfilesystem.py	90.22% <84.61%> (+0.22%)	⬆️
sdks/python/apache_beam/utils/interactive_utils.py	87.80% <0.00%> (-7.32%)	⬇️
...hon/apache_beam/runners/direct/test_stream_impl.py	94.02% <0.00%> (-2.24%)	⬇️
...ks/python/apache_beam/runners/worker/data_plane.py	87.50% <0.00%> (-1.71%)	⬇️
sdks/python/apache_beam/io/source_test_utils.py	88.01% <0.00%> (-1.39%)	⬇️
sdks/python/apache_beam/internal/metrics/metric.py	90.00% <0.00%> (-1.00%)	⬇️
...pache_beam/runners/interactive/interactive_beam.py	75.60% <0.00%> (-0.98%)	⬇️
...runners/interactive/display/pcoll_visualization.py	85.85% <0.00%> (-0.51%)	⬇️
...hon/apache_beam/runners/worker/bundle_processor.py	93.26% <0.00%> (-0.50%)	⬇️
...nners/portability/fn_api_runner/worker_handlers.py	79.44% <0.00%> (-0.35%)	⬇️
... and 3 more

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[aaltay]

@ihji - a friendly ping to review this PR.

[mlhamel]

@aaltay @ihji - Friendly ping, what do you think of the implementation. Does it make sense ?

[aaltay]

@chamikaramj @ihji - Who could help with reviewing this PR?

[ihji]

Not sure about making this change if it's mostly for easier testing. Do you have any other use cases in mind?

[mlhamel]

It's mostly for testing but if you feel it's not enought for introducing that type of pattern feel free to close that PR and the corresponding issue https://issues.apache.org/jira/browse/BEAM-13250.

I tend to prefer having a predefined of injecting those dependencies but I'm sure we can find alternatives for better testing our flow.

[aaltay]

Closing based on the comment thread. Feel free to re-open if you disagree.