[Optimizers] Multifidelity algorithms should check for min_budget == 0

[eddiebergman]

Right now, we get a ZeroDivisionError with SuccessiveHalving based algorithms because the fidelity parameter has a lower bound of 0 in a testing setup.

Moreover, perhaps we should explicitly check that it's positive all the time? This might belong in the search space instead though.

neps/neps/optimizers/multi_fidelity/successive_halving.py

Lines 121 to 123 in 82b4890

	self.stopping_rate_limit = np.floor(
	np.log(self.max_budget / self.min_budget) / np.log(self.eta)
	).astype(int)