Take fast path only for delegate types not Delegate/MulticastDelegate (case 1085270)

See upstream PR: mono#11182

Author: joncham

mono/metadata/icall.c

@@ -3950,7 +3950,7 @@ mono_class_get_methods_by_name (MonoClass *klass, const char *name, guint32 bfla
 		compare_func = (ignore_case) ? mono_utf8_strcasecmp : strcmp;
 
 	/* An optimization for calls made from Delegate:CreateDelegate () */
-	if (klass->delegate && name && !strcmp (name, "Invoke") && (bflags == (BFLAGS_Public | BFLAGS_Static | BFLAGS_Instance))) {
+	if (klass->delegate && klass != mono_defaults.delegate_class && klass != mono_defaults.multicastdelegate_class&& name && !strcmp (name, "Invoke") && (bflags == (BFLAGS_Public | BFLAGS_Static | BFLAGS_Instance))) {
 		method = mono_get_delegate_invoke (klass);
 		g_assert (method);