DisposeSentinel is used to automatically detect memory leaks.
The DisposeSentinel class is used by native containers to automatically track memory leaks, and report them to the user. The DisposeSentinel is a managed object that is only referenced by the native container that holds the native data that we don't want to leak. The DisposeSentinel finalizer, which is invoked when there are not more references to the native container that owns it, checks if the referenced data has been disposed correctly or not, and in case it is not, it logs an error containing the information about when the initial allocation happened.
The DisposeSentinel class is available only when ENABLE_UNITY_COLLECTIONS_CHECKS is defined.
Additional resources: the example in NativeContainerAttribute.