patch 8.2.2272: Vim9: extend() can violate the type of a variable

Problem:    Vim9: extend() can violate the type of a variable.
Solution:   Add the type to the dictionary or list and check items against it.
            (closes #7593)
diff --git a/src/structs.h b/src/structs.h
index 102be0e..e204510 100644
--- a/src/structs.h
+++ b/src/structs.h
@@ -1481,6 +1481,7 @@
 	    int		lv_idx;		// cached index of an item
 	} mat;
     } lv_u;
+    type_T	*lv_type;	// allocated by alloc_type()
     list_T	*lv_copylist;	// copied list used by deepcopy()
     list_T	*lv_used_next;	// next list in used lists list
     list_T	*lv_used_prev;	// previous list in used lists list
@@ -1544,6 +1545,7 @@
     int		dv_refcount;	// reference count
     int		dv_copyID;	// ID used by deepcopy()
     hashtab_T	dv_hashtab;	// hashtab that refers to the items
+    type_T	*dv_type;	// allocated by alloc_type()
     dict_T	*dv_copydict;	// copied dict used by deepcopy()
     dict_T	*dv_used_next;	// next dict in used dicts list
     dict_T	*dv_used_prev;	// previous dict in used dicts list