DOC: Update array API docs after changes in logic and design

[david-cortes-intel]

Description

There have been several changes in how array API support works in scikit-learn and fixes in sklearnex that now make some statements in the documentation obsolete.

For example, by now all public-facing attributes of array API estimators should be of array API classes, which was not the case before, and implementation of 'everything follows X' logic is in progress, so now more potential input combinations are allowed.

The documentation will need further updates after implementing move_to.

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Checklist:

Completeness and readability

• I have updated the documentation to reflect the changes or created a separate PR with updates and provided its number in the description, if necessary.
• Git commit message contains an appropriate signed-off-by string (see CONTRIBUTING.md for details).
• I have resolved any merge conflicts that might occur with the base branch.

Testing

• I have run it locally and tested the changes extensively.
• All CI jobs are green or I have provided justification why they aren't.