Refactor RabbitMQ functionality to new project

Moved RabbitMQ-related functionality from the
`DigitalData.MessagingService.Infrastructure` project to a new
dedicated project/namespace `DigitalData.MessagingService.RabbitMQ`.

- Updated `DependencyInjection.cs` to use the new namespace.
- Added a project reference to `RabbitMQ.csproj` in the
  `Infrastructure.csproj` file.
- Removed `RabbitMqConfiguration.cs` and `RabbitMqConnectionFactory.cs`
  from the `Infrastructure` project.
- Updated namespaces in `OutgoingEmailConsumer.cs`,
  `OutgoingEmailPublisher.cs`, and `AsyncInitWorker.cs` to use
  `DigitalData.MessagingService.RabbitMQ`.

This refactor improves modularity, maintainability, and separation
of concerns by isolating RabbitMQ functionality in its own project.

src/DigitalData.MessagingService.Infrastructure/Queue/OutgoingEmailConsumer.cs

@@ -1,7 +1,7 @@
 using System.Text;
 using System.Text.Json;
 using DigitalData.MessagingService.Application.Common.Interfaces;
-using DigitalData.MessagingService.Infrastructure.Messaging;
+using DigitalData.MessagingService.RabbitMQ;
 using Microsoft.Extensions.Logging;
 using Microsoft.Extensions.Options;
 using RabbitMQ.Client;