Add a pre-check for the number of canonical equivalent permutations in j.u.r.Pattern

The computation of the number of canonical equivalent permutations requires a pre-check to ensure the correctness of the result in the `int` range.

A check failure indicates that the computation would overflow the `int` range. As a consequence, there's no point in generating the permutations, as that would later lead to an `OutOfMemoryError`.

From a logical perspective, however, a failure still indicates an `OutOfMemoryError` condition, although not a physical one. Thus, `OutOfMemoryError` is thrown pre-emptively with a descriptive message.