Add settings change notifier

[wmontwe]

This introduces a new settings change notification system to the project. The main changes include adding a publish/subscribe pattern with a broker and publisher for settings changes, updating existing classes to use this new system, and adding tests for the new functionality.

The drawer is now immediatelly updated whenever a setting is changed.

Resolves #8765

[cketti]

There's a race condition in DefaultSettingsChangeBroker.

[cketti]

This accesses subscribers without synchronizing on lock. If a subscriber is removed in one thread while this is iterating over subscribers in another thread, a ConcurrentModificationException could be thrown.

The problem can be avoided by also wrapping this method body in synchronized(lock) { … } or by using CopyOnWriteArraySet which can be used without any manual locking/synchronization.

[wmontwe]

I avoided synchronizing this method to balance performance with the low likelihood of concurrent modifications in our use case. However, I agree that the current approach is not robust and should be replaced with a more comprehensive solution in the future.

The CopyOnWriteArraySet is a Java only dependency and I opted for a Kotlin specific alternative.

[wmontwe]

I added a lock around the receivers to avoid ConcurrentModificationException