[ENH] ensure that all_objects always returns (class name/class) pairs

[fkiraly]

all_objects in vanilla form returns a list of (str, BaseObject) pairs.

Currently, these pairs do not need to satisfy the condition that for the pair (name, klass) it holds that name = klass.__name__.
An example of this case is when a class is assigned to a variable name other than the class name. In that case name is the variable name, not the class name. E.g., doing sth like this

class Test:
    def __init__(self, stuff):
        more_stuff

test2 = Test

results in the class Test being returned twice, once with name test2 and once with name Test.

This can be quite confusing and violate an interface contract that is not strictly stated as guaranteed, but may be assumed by users of the utility (and, apparently, by the status quo in sktime as well as the failing tests in the attempted refactor PR sktime/sktime#3777 e.g., see the line assert estimator[0] == estimator[1].__name__ in test_all_estimators_by_scitype)

I would argue that it should always hold that name = klass.__name__ for the returned pairs for that reason.

The alternative solution to this issue would be to make crystal clear in the docstring what is being guaranteed, and what not, about the name/estimator pairs returned.

[codecov-commenter]

Codecov Report

Merging #115 (b3107ef) into main (471000d) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##             main     #115   +/-   ##
=======================================
  Coverage   77.93%   77.93%           
=======================================
  Files          23       23           
  Lines        1867     1867           
=======================================
  Hits         1455     1455           
  Misses        412      412           

Impacted Files	Coverage Δ
skbase/lookup/_lookup.py	95.48% <ø> (ø)

Help us with your feedback. Take ten seconds to tell us how you rate us. Have a feature suggestion? Share it here.

[RNKuhns]

Seems reasonable. Hadn't considered the case where class was assigned to variable. LGTM.