DOC-619 Add pydata version switcher

[neverett]

Why are the changes needed?

Allow readers to choose the docs version that corresponds to the version of Flyte they are using.

What changes were proposed in this pull request?

Adds switcher.json and configuration changes in conf.py

How was this patch tested?

Tested locally.

Screenshots

Check all the applicable boxes

• I updated the documentation accordingly.
• All new and existing tests passed.
• All commits are signed-off.

Docs link

https://flyte--5846.org.readthedocs.build/en/5846/

[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 36.35%. Comparing base (a8b16a5) to head (8a1f9fe).

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #5846      +/-   ##
==========================================
+ Coverage   34.48%   36.35%   +1.86%     
==========================================
  Files        1138     1304     +166     
  Lines      102742   110148    +7406     
==========================================
+ Hits        35434    40040    +4606     
- Misses      63634    65941    +2307     
- Partials     3674     4167     +493     

Flag	Coverage Δ
unittests-datacatalog	51.37% <ø> (ø)
unittests-flyteadmin	55.57% <ø> (-0.04%)	⬇️
unittests-flytecopilot	12.17% <ø> (ø)
unittests-flytectl	62.26% <ø> (?)
unittests-flyteidl	7.17% <ø> (ø)
unittests-flyteplugins	53.35% <ø> (ø)
unittests-flytepropeller	42.02% <ø> (ø)
unittests-flytestdlib	55.37% <ø> (+0.02%)	⬆️

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