patch 8.2.4670: memory allocation failures for new tab page not tested

Problem:    Memory allocation failures for new tab page not tested.
Solution:   Add tests with failing memory allocation. (Yegappan Lakshmanan,
            closes #10067)

src/alloc.h

@@ -40,6 +40,9 @@ typedef enum {
     aid_sign_getplaced_list,
     aid_insert_sign,
     aid_sign_getinfo,
-    aid_buflistnew_bvars,
+    aid_newbuf_bvars,
+    aid_newwin_wvars,
+    aid_newtabpage_tvars,
+    aid_blob_alloc,
     aid_last
 } alloc_id_T;