[SearchSpace] Allow None/ bool as a valid value in Categorical/Constant

[eddiebergman]

Right now, the only accepted values are Iterable[float | int | str] and the default is the same, i.e. float | int | str | None = None.

There's no real restriction for this other than it needs to be tracked down where things like the following might happen, if default... (which would also not work for 0 fyi), and replace them with if default is not NotSet where NotSet follows then Sentinal pattern (it's just NotSet = object() and you check if it was not set by doing if default is NotSet)

For example, one thing that would need to change is the following:

neps/neps/search_spaces/search_space.py

Lines 735 to 737 in 82b4890

	if hp.default is None:
	if not ignore_missing_defaults:
	raise ValueError(f"No defaults specified for {hp} in the space.")

EDIT: apparently I already did some of this a while back but didn't complete it nor test it...

neps/neps/search_spaces/search_space.py

Lines 795 to 798 in 82b4890

	for hp_key, current_hp in self.hyperparameters.items():
	new_hp_value = hyperparameters.get(hp_key, NotSet)
	if isinstance(new_hp_value, _NotSet):
	continue