Refactor SQL execution classes into new namespace

Restructure and refactor classes related to SQL execution within the `EnvelopeGenerator.Infrastructure` namespace. Key changes include:
- Added `EnvelopeGenerator.Infrastructure.Executor` namespace.
- Moved and redefined `Query`, `QueryExtension`, `SQLExecutor`, `SQLExecutorBaseEntity`, and `SQLExecutorParams` classes to the new namespace.
- Maintained existing functionality while improving code organization and clarity.

EnvelopeGenerator.Infrastructure/DependencyExtensions.cs

@@ -8,6 +8,7 @@ using EnvelopeGenerator.Domain.Entities;
 using DigitalData.Core.Infrastructure.AutoMapper;
 using EnvelopeGenerator.Application.Contracts.SQLExecutor;
 using Microsoft.Extensions.Configuration;
+using EnvelopeGenerator.Infrastructure.Executor;
 
 namespace EnvelopeGenerator.Infrastructure;