gh-36018: Fix tests with singular 4.3.2p4
Due to changes in the output of `hilb` in singular 4.3.2p4 (it now
outputs a polynomial instead of a list of monomials and coefficients to
debug), some tests are failing.
Additionally, the problematic `hilbert_numerator` example now correctly
throws an overflow error instead of giving a wrong answer. We mark it as
`known bug` so the test passes with older versions of singular, the
label can be removed once we require 4.3.2p4.
URL: https://github.com/sagemath/sage/pull/36018
Reported by: Antonio Rojas
Reviewer(s): Matthias Köppe
