Add type validation to regex constraint

[RenderMichael]

Fixes #4484
tests like

Assert.That(1, Does.Not.Match("[A-Z]"));
Assert.That((string?)null, Does.Not.Match("[A-Z]"));

will no longer pass.

Bonus performance for converting regex.Match(...).Success to regex.IsMatch(...)

[manfred-brands]

Thanks @RenderMichael Your code changes are functionally fine.
My nitpicks are purely to get a more consistent code base.

[RenderMichael]

@manfred-brands thanks for the review! feedback merged, PTAL

[manfred-brands]

Thanks for that. Nothing further.