fix: Correctly dispose of everything in adapter's OnDestroy

[simon-lemay-unity]

MTT-2305

Some of the native containers used by the adapter are not disposed of correctly when destroying the UnityTransport component. They're disposed of correctly when shutting down gracefully (through the Shutdown method), but not if the component is destroyed without shutting it down. To fix this, we now dispose of everything in OnDestroy too.

Changelog

com.unity.netcode.adapter.utp

• Fixed: Fixed issue with native collections not all being disposed of when destroying the component without shutting it down properly. This would result in errors in the console and memory leaks.

Testing and Documentation

• No tests have been added.
• No documentation changes or additions were necessary.