fix many custom mro() edge cases and improve code quality (#22735)

Patch by Eldar Abusalimov.
diff --git a/Misc/ACKS b/Misc/ACKS
index 733683d..65518db 100644
--- a/Misc/ACKS
+++ b/Misc/ACKS
@@ -16,6 +16,7 @@
 Rajiv Abraham
 David Abrahams
 Marc Abramowitz
+Eldar Abusalimov
 Ron Adam
 Anton Afanasyev
 Ali Afshar