Tracking DF 41 release

[Michael-J-Ward]

Tracking issue for release of DF 41. Please let us know if there's a particular issue you're waiting on!

• Upgrade deps to datafusion 41 #802
• Enhance Expr.cast() to accept python types #753
• clarify separation between rust code and python wrappers #779
• Incorporate unified Aggregate / Window function builder #780
• Cannot create a SessionContext with only a SessionConfig #826
• Implement Arrow PyCapsule Interface #752
• Feature/expose when function #836
• Run ruff format in CI #837
• Set of small features #839 which closes
  • Render tables using html in notebooks. #713
  • Add DataFrame transform function #807
  • Support array expressions for __getitem__ #810

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Require upstream issues to be resolved, and so will not be included in 41

• Error on dataframe count using arrow dataset #800
• Expose additional regexp functions #803

[timsaucer]

I'd like to include:

• Implement Arrow PyCapsule Interface #752
• Feature/expose when function #836
• Run ruff format in CI #837
• Set of small features #839 which closes Render tables using html in notebooks. #713 Add DataFrame transform function #807 and Support array expressions for __getitem__ #810

[Michael-J-Ward]

@timsaucer - added