We're aiming to make TypeInfo instances unique - no two TypeInfo
instances within a given model should refer to the same type. This will
allow us to use simple reference equality for comparing types.
The C# functions for GetGenericParameters/GetGenericArguments use
Type[], not lists, so we should conform to that.
Also fix the definition of IsGenericTypeDefinition - because it's
possible for a class to be instantiated with all generic parameters.
Replace the deeply nested ternaries in TypeInfo with if-statements for
clarity.
Remove in/out from CSharpName, keeping it only on immediate type params
in CSharpTypeDeclarationName (refactored to a method).
Rearrange name-related properties and methods to group them all together
into a region for easier navigation.
