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/Executor/SQLExecutorBaseEntity.cs

@@ -0,0 +1,31 @@
+using EnvelopeGenerator.Application.Contracts.SQLExecutor;
+using Microsoft.EntityFrameworkCore;
+using Microsoft.Extensions.DependencyInjection;
+using Microsoft.Extensions.Options;
+
+namespace EnvelopeGenerator.Infrastructure.Executor;
+
+public sealed class SQLExecutor<T> : SQLExecutor, ISQLExecutor<T> where T : class
+{
+    private readonly EGDbContext _context;
+
+    private readonly IServiceProvider _provider;
+
+    public SQLExecutor(EGDbContext context, IServiceProvider provider, IOptions<SQLExecutorParams> options) : base(provider, options)
+    {
+        _context = context;
+        _provider = provider;
+    }
+
+    public IQuery<T> Execute(string sql, CancellationToken cancellation = default, params object[] parameters)
+        => _context
+            .Set<T>()
+            .FromSqlRaw(sql, parameters)
+            .ToQuery();
+
+    public IQuery<T> Execute<TSQL>(CancellationToken cancellation = default, params object[] parameters) where TSQL : ISQL<T>
+    {
+        var sql = _provider.GetRequiredService<TSQL>();
+        return Execute(sql.Raw);
+    }
+}