Name of the listener. Used for logging. Must not throw.

Called after the state of a health element has changed.

Implementations must be thread-safe in the sense that multiple notifications can run concurrently. Implementations must not block and should not execute significant computations as part of this call. In particular, it is wrong to assume that the listener has finished its updates by the time this method returns.

We explicitly do NOT pass along the new state of the health element nor the health element itself. Instead, the listener must query the current state using HealthElement.getState. This ensures that we do not need to synchronize concurrent updates and notifications; the state obtained HealthElement.getState is guaranteed to be at least as up to date as the notification.