[ENH] allow arbitrary base class in all_objects

[fkiraly]

This PR extends all_objects to allow an arbitrary base class - currently, it only lists classes inheriting from skbase all_objects. With the change in this PR, something like this will give the expected results - of all estimators in sklearn:

from skbase.lookup import all_objects
from sklearn.base import BaseEstimator

all_objects(BaseEstimator, package_name="sklearn", modules_to_ignore=["tests"], as_dataframe=True)

Minor changes also contained:

• removes unused args exclude_estimators and ignore_modules