Currently, we are leaking HttpEngine from KtorNetworkTransport and various dispatchers when Realms are being closed.

This can cause problems as surfaced here https://github.com/realm/realm-kotlin/issues/733 where the hypothesis is the running dispatchers prevent the JVM from closing.

As discussed here https://github.com/realm/realm-kotlin/pull/817#issue-1220927930, the current approach where these resources are created by Configuration objects and potentially shared between many Realms/App make it impossible to safely stop them.

Most likely we need to refactor these code paths, so the resources are created lazily and owned by each App / Realm, so they can safely be torn down when those classes are closed.