Caching of initializeMemberResolvers seems to cause a bug

For contracts that contain both a .cdc source file, with Cadence code,
and with some functions being implemented natively, the GetMembers()
does not return the natively implemented members.

runtime/sema/type.go

@@ -4262,9 +4262,8 @@ func (t *CompositeType) GetMembers() map[string]MemberResolver {
 }
 
 func (t *CompositeType) initializeMemberResolvers() {
-	t.memberResolversOnce.Do(func() {
+	f := func() {
 		memberResolvers := MembersMapAsResolvers(t.Members)
-
 		// Check conformances.
 		// If this composite type results from a normal composite declaration,
 		// it must have members declared for all interfaces it conforms to.
@@ -4281,7 +4280,12 @@ func (t *CompositeType) initializeMemberResolvers() {
 			})
 
 		t.memberResolvers = withBuiltinMembers(t, memberResolvers)
-	})
+	}
+	t.memberResolversOnce.Do(f)
+
+	if len(t.memberResolvers) != t.Members.Len() {
+		f()
+	}
 }
 
 func (t *CompositeType) FieldPosition(name string, declaration ast.CompositeLikeDeclaration) ast.Position {