singularLocus for noncommutative inputs

`singularLocus` currently allows as input ideals from noncommutative rings (e.g. WeylAlgebras), and returns meaningless results. Instead, it should return an error. Otherwise, those working with D Modules might accidentally use singularLocus when they mean to use the similarly named `singLocus` from the Dmodules package (`singLocus` will be renamed soon).

Start at the singularLocus entry point and trace how it accepts ideals from noncommutative rings such as WeylAlgebras. Compare its intended behavior with the issue’s distinction from singLocus in the Dmodules package. Done means singularLocus returns an error for noncommutative inputs while preserving its commutative behavior.

Written by the indexing model from the issue text.