chore: rename `message_queue_too_long` error reason to `mailbox_overflow`

`mailbox_overflow` is consistent with the corresponding config parameter:
 'force_shutdown.max_mailbox_size'

apps/emqx_utils/src/emqx_utils.erl

@@ -273,7 +273,7 @@ check_oom(Pid, #{
             ok;
         [{message_queue_len, QLen}, {total_heap_size, HeapSize}] ->
             do_check_oom([
-                {QLen, MaxQLen, message_queue_too_long},
+                {QLen, MaxQLen, mailbox_overflow},
                 {HeapSize, MaxHeapSize, proc_heap_too_large}
             ])
     end.

apps/emqx_utils/test/emqx_utils_SUITE.erl

@@ -150,7 +150,7 @@ t_check(_) ->
     ?assertEqual(ok, emqx_utils:check_oom(Policy)),
     [self() ! {msg, I} || I <- lists:seq(1, 6)],
     ?assertEqual(
-        {shutdown, #{reason => message_queue_too_long, value => 11, max => 10}},
+        {shutdown, #{reason => mailbox_overflow, value => 11, max => 10}},
         emqx_utils:check_oom(Policy)
     ).
 

changes/ce/fix-12766.en.md

@@ -0,0 +1,3 @@
+Rename `message_queue_too_long` error reason to `mailbox_overflow`
+
+`mailbox_overflow` is consistent with the corresponding config parameter: `force_shutdown.max_mailbox_size`.