Optimize empty CopyOnWriteArrayList allocations

We have seen the cases in production where lots of empty CopyOnWriteArrayList-s take a considerable amount of memory/instances. We can follow the example how other collections handled these cases, and initialize with a shared empty array instance.

See e.g. JDK-8035584 for ArrayList: https://github.com/openjdk/jdk/commit/e0c3c7a07de23cca0ee938eb64af973d567fcdaf