RouteGroupConstraint should only be added once for non attribute routed actions

[javiercn]

Given the following controllers and actions

private class MixedAttributeRouteController
{
    [HttpGet("Index")]
    public void Index() { }

    [HttpGet("Edit")]
    public void Edit() { }

    public void AnotherNonAttributedAction() { }
}

[MyRouteConstraint(blockNonAttributedActions: true)]
[MySecondRouteConstraint(blockNonAttributedActions: true)]
private class ConstrainedController
{
    public void ConstrainedNonAttributedAction() { }
}

AnotherNonAttributedAction gets added once RouteGroupConstraint for each RouteDataConstraint defined in a Controller. So in the above example it will end up with two route data constraints.