Every TypeSymbolWithAnnotations should have an explicit NonNullTypes context #28766
Description
We currently have some overload of Create which default to placeholder contexts (NonNullTypesTrueContext or NonNullTypesFalseContext).
Those overloads should be removed and proper/explicit contexts should be used in most places, if not all.
' The NonNullTypes context for nested tuple types is using a dummy rather than actual context from surrounding code.
' This does not affect `IsNullable`, but it affects `IsAnnotatedWithNonNullTypesContext`, which is used in comparisons.
' So when we copy modifiers (re-applying nullability information, including actual NonNullTypes context), we make the comparison fail.
' I think the solution is to never use a dummy context, even for value types.
<Fact(Skip:="PROTOTYPE(NullableReferenceTypes): Hitting assertion in CopyTypeCustomModifiers")>
Public Sub TupleNamesFromCS001()
Relates to #28487