Merge branch 'bugfix/heap_psram_fill_v4.0' into 'release/v4.0'

heap: Only fill new heaps with FREE_FILL_PATTERN if Comprehensive poisoning is on (v4.0)

See merge request espressif/esp-idf!8491

components/heap/multi_heap_poisoning.c

@@ -306,9 +306,11 @@ void *multi_heap_get_block_owner(multi_heap_block_handle_t block)
 
 multi_heap_handle_t multi_heap_register(void *start, size_t size)
 {
+#ifdef SLOW
     if (start != NULL) {
         memset(start, FREE_FILL_PATTERN, size);
     }
+#endif
     return multi_heap_register_impl(start, size);
 }