Don't write warning about uninitialized mutex if there is a memory leak

Part of:
MDEV-21056 Assertion `global_status_var.global_memory_used == 0'
failed upon shutdown after query with DEFAULT on a geometry
field

Fixed by changing the ASSERT for memory leaks to a printf() on
stderr. This has needed as all mutex in mysys has been deleted and we
can't call functions like my_open() anymore.

Also added printing of leaks if safemalloc is used (like we do in 10.5)

sql/mysqld.cc

@@ -2172,13 +2172,12 @@ static void mysqld_exit(int exit_code)
   shutdown_performance_schema();        // we do it as late as possible
 #endif
   set_malloc_size_cb(NULL);
-  if (opt_endinfo && global_status_var.global_memory_used)
-    fprintf(stderr, "Warning: Memory not freed: %ld\n",
-            (long) global_status_var.global_memory_used);
-  if (!opt_debugging && !my_disable_leak_check && exit_code == 0 &&
-      debug_assert_on_not_freed_memory)
+  if (global_status_var.global_memory_used)
   {
-    DBUG_ASSERT(global_status_var.global_memory_used == 0);
+    fprintf(stderr, "Warning: Memory not freed: %lld\n",
+            (longlong) global_status_var.global_memory_used);
+    if (exit_code == 0)
+      SAFEMALLOC_REPORT_MEMORY(0);
   }
   cleanup_tls();
   DBUG_LEAVE;