Deprecate methods and streamline controller code

Added [Obsolete("Use MediatR")] attribute to several methods
across `DocumentController`, `HomeController`,
`TestConfigController`, `TestDocumentReceiverElementController`,
and `TestEnvelopeController` to indicate they should no longer
be used.

Refactored constructors in `TestConfigController` and
`TestEnvelopeController` to remove unnecessary empty blocks.

Improved formatting and structure of the `GetAll` method in
`TestEnvelopeController` for better clarity while maintaining
functionality.

Updated `Program.cs` to suppress warnings about obsolete
types/members during service registrations, indicating a
transition to newer implementations.

EnvelopeGenerator.Web/Controllers/Test/TestDocumentReceiverElementController.cs

@@ -4,6 +4,7 @@ using EnvelopeGenerator.Domain.Entities;
 
 namespace EnvelopeGenerator.Web.Controllers.Test;
 
+[Obsolete("Use MediatR")]
 public class TestDocumentReceiverElementController : TestControllerBase<IDocumentReceiverElementService, DocumentReceiverElementDto, DocumentReceiverElement, int>
 {
     public TestDocumentReceiverElementController(ILogger<TestDocumentReceiverElementController> logger, IDocumentReceiverElementService service) : base(logger, service)