patch 8.2.1691: Vim9: list<any> is not accepted where list<number> is expected

Problem:    Vim9: list<any> is not accepted where list<number> is expected.
Solution:   Add functions to allocate and free a type_T, use it in
            ISN_CHECKTYPE. (closes #6959)

src/vim9.h

@@ -207,7 +207,7 @@ typedef struct {
 
 // arguments to ISN_CHECKTYPE
 typedef struct {
-    vartype_T	ct_type;
+    type_T	*ct_type;
     int		ct_off;	    // offset in stack, -1 is bottom
 } checktype_T;