feat: Added Specification tests for DbDataReader

Author: KirillKurdyukov

src/Ydb.Sdk/src/Ado/ThrowHelper.cs

@@ -8,4 +8,9 @@ internal static T ThrowInvalidCast<T>(YdbValue ydbValue)
     {
         throw new InvalidCastException($"Field type {ydbValue.TypeId} can't be cast to {typeof(T)} type.");
     }
+
+    internal static void ThrowIndexOutOfRangeException(int columnCount)
+    {
+        throw new IndexOutOfRangeException("Ordinal must be between 0 and " + (columnCount - 1));
+    }
 }

src/Ydb.Sdk/src/Ado/YdbCommand.cs

@@ -52,9 +52,7 @@ public override async Task<int> ExecuteNonQueryAsync(CancellationToken cancellat
     {
         await using var dataReader = await ExecuteReaderAsync(CommandBehavior.Default, cancellationToken);
 
-        var data = await dataReader.ReadAsync(cancellationToken)
-            ? dataReader.IsDBNull(0) ? null : dataReader.GetValue(0)
-            : null;
+        var data = await dataReader.ReadAsync(cancellationToken) ? dataReader.GetValue(0) : null;
 
         while (await dataReader.NextResultAsync(cancellationToken))
         {

src/Ydb.Sdk/src/Ado/YdbConnection.cs

@@ -173,7 +173,7 @@ public override string ConnectionString
 
     internal YdbDataReader? LastReader { get; set; }
     internal string LastCommand { get; set; } = string.Empty;
-    internal bool IsBusy => LastReader is { IsClosed: false };
+    internal bool IsBusy => LastReader is { IsOpen: true };
     internal YdbTransaction? CurrentTransaction { get; private set; }
 
     public override string DataSource => string.Empty; // TODO