Fix: Inaccurate Attribute Listing with dir(obj)

[MiguelParece]

Inaccurate Attribute Listing with__dir__(obj) in classes with conditional methods, I overwrote the python method dir() in all the classes that contain conditional methods

Fixes #28558

[github-actions]

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[betatim]

Thanks for tackling this and making your first contribution to scikit-learn!

Some thoughts on what to do next:

• add a test to make sure that if a class as a conditional method it also has a modified __dir__. And that the reverse is also true: if there are no conditional methods, there should be no __dir__ defined
  • the tricky bit here is to write the test as a common test so that we don't have to make a list of classes
• add a test to check that the result of calling __dir__ is correct, for all possible conditions of available_if
• add a comment to the __dir__ implementations that explains why it is there
• no (deprecation) warnings are raised when triggering attribute listing
  • deprecated attributes should be listed
• bonus: find a way to reduce the need for defining __dir__ everywhere, but maybe this isn't possible

[lesteve]

Not sure what is causing the CI error, I guess your __dir__ implementation iterates over all the attributes and raises a warning for deprecated attributes somehow. Not sure why it works in one CI build and not the other ...

Maybe try to debug this, and maybe catching the warnings inside __dir__ could be a stop-gap solution, at least for now and we can rediscuss how to do this in a better way when we are closer to review this in more details.

[MiguelParece]

@betatim all good ?