bpo-42519: Replace PyMem_MALLOC() with PyMem_Malloc() (GH-23586)

No longer use deprecated aliases to functions:

* Replace PyMem_MALLOC() with PyMem_Malloc()
* Replace PyMem_REALLOC() with PyMem_Realloc()
* Replace PyMem_FREE() with PyMem_Free()
* Replace PyMem_Del() with PyMem_Free()
* Replace PyMem_DEL() with PyMem_Free()

Modify also the PyMem_DEL() macro to use directly PyMem_Free().
diff --git a/Objects/setobject.c b/Objects/setobject.c
index af8ee03..79e8451 100644
--- a/Objects/setobject.c
+++ b/Objects/setobject.c
@@ -289,7 +289,7 @@
     }
 
     if (is_oldtable_malloced)
-        PyMem_DEL(oldtable);
+        PyMem_Free(oldtable);
     return 0;
 }
 
@@ -424,7 +424,7 @@
     }
 
     if (table_is_malloced)
-        PyMem_DEL(table);
+        PyMem_Free(table);
     return 0;
 }
 
@@ -484,7 +484,7 @@
         }
     }
     if (so->table != so->smalltable)
-        PyMem_DEL(so->table);
+        PyMem_Free(so->table);
     Py_TYPE(so)->tp_free(so);
     Py_TRASHCAN_END
 }