Add function to selectively remove estimators from the registry

[mgxd]

What would you like to see added in this software?

This has come up in https://github.com/nipreps/fmriprep/pull/3060

To avoid filtering out estimators multiple times, we should incorporate a selective purge in the same spirit as https://github.com/nipreps/sdcflows/blob/375dd7a024abcd5d4d2b282241a037d76f9719e6/sdcflows/fieldmaps.py#L493-L496 to avoid accessing private _estimators.

Do you have any interest in helping implement the feature?

Yes

Additional information / screenshots

No response