ECMA-335 addendum should mention that null managed pointers are legal #69690
Description
Ref: https://github.com/dotnet/runtime/blob/main/docs/design/specs/Ecma-335-Augments.md
We expose APIs like Unsafe.IsNullRef and Unsafe.NullRef, which imply that nullptr managed pointers are supported across our runtimes. However, ECMA-335, Sec. II.14.4.2 and III.1.1.5.2 both explicitly state that nullptr managed pointers are disallowed. ECMA should be updated.