Add an inplace=False/True keyword argument to __call__ on fitters to allow in-place modification of models - #17033

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I'm not a modeling maintainer, but I like this addition!

This seems like the nicer approach! I guess one small suggestion (but might as well wait for proper review), is to add a * to ensure the new argument is keyword-only.

Done!

This looks good. A couple of comments

• Can you edit the Returns sections in the docstrings to clarify that the returned model is not always a copy
• Should the inplace parameter be passed to the FittingWithOutlierRemoval? Speeding up this one will be a good thing too.

Also I wonder if a note should be added to the Performance tips section in the documentation.
https://docs.astropy.org/en/latest/modeling/performance.html

@nden - I've now:

• Added a performance tip
• Updated the Returns sections in the docstrings for all the fitters
• Added an explicit inplace= option to FittingWithOutlierRemoval (in fact the option was passed through anyway via **kwargs but I think it's clearer this way

pre-commit.ci autofix

@nden - this should be ready, the CI failures are unrelated.

Rebased