Non-generic CompareTo's ArgumentException message breaks on a nested generic argument #273

Part 1 of #258, split out so it can be closed by its own PR. Part 2 of #258, the YearMonthRange exclusive infinity) load, stays on #258.

Problem

RangeOrder.TypeName strips the arity from Type.Name at its backtick. A type nested inside a generic one, such as List<int>.Enumerator, is generic but has no backtick in its own name. So ((IComparable)range).CompareTo(new List<int>().GetEnumerator()) throws ArgumentOutOfRangeException: length ('-1') must be a non-negative value instead of the intended ArgumentException naming both types. Found by the final pre-release analysis on add665c.

Done when

A foreign nested generic argument gets the intended message, and a test holds it.