Added hook to lifecycle events

[akbashev]

Ability to listen to actors lifecycles in a plugin.

Motivation:

Plugins give an option to extend system with some logic. Problem is sometimes you need to hook into actor's creation/deletion, which currently is impossible. As an example—for actor recovery we need to restore state when it's created and ready for cluster system, which can be done by some potential EventSourcingJournal.

By adding simple hook protocol we can enable this.

Modifications:

• PluginActorLifecycleHook protocol
• additional actorLifecycleHooks in plugins settings
• inside ClusterSystem's actorReady and resignID are called for each hookable plugin added to the system.

[akbashev]

Still not sure about PluginActorLifecycleHook name 😅

[ktoso]

@swift-server-bot test this please

[ktoso]

@swift-server-bot add to allowlist