Move event handler interfaces to the abstraction package.

framework/src/Volo.Abp.EventBus/Volo/Abp/EventBus/IEventHandler.cs → framework/src/Volo.Abp.EventBus.Abstractions/Volo/Abp/EventBus/IEventHandler.cs

@@ -3,7 +3,7 @@ using Volo.Abp.EventBus.Distributed;
 namespace Volo.Abp.EventBus;
 
 /// <summary>
-/// Undirect base interface for all event handlers.
+/// Indirect base interface for all event handlers.
 /// Implement <see cref="ILocalEventHandler{TEvent}"/> or <see cref="IDistributedEventHandler{TEvent}"/> instead of this one.
 /// </summary>
 public interface IEventHandler

framework/src/Volo.Abp.EventBus/Volo/Abp/EventBus/Local/ILocalEventHandler.cs → framework/src/Volo.Abp.EventBus.Abstractions/Volo/Abp/EventBus/Local/ILocalEventHandler.cs

@@ -1,8 +1,8 @@
 using System.Threading.Tasks;
 
+// ReSharper disable once CheckNamespace (Keeping for backward compability)
 namespace Volo.Abp.EventBus;
 
-//TODO: Move to the right namespace in v3.0
 public interface ILocalEventHandler<in TEvent> : IEventHandler
 {
     /// <summary>