fix: ReadBytesExact was calling itself instead of r.ReadBytes()

Infinite recursion caused StackOverflowException on every query.
ReadBytesExact must call r.ReadBytes(count) as the base read,
then check the returned length.

Co-authored-by: Copilot <223556219+Copilot@users.noreply.github.com>

Author: vkuttyp

src/SqlDotnetty.MsSql/Tds/TdsDecoder.cs

@@ -803,7 +803,7 @@ private static SqlValue ReadDateTimeOffset(BinaryReader r, byte scale)
     private static byte[] ReadBytesExact(BinaryReader r, int count)
     {
         if (count == 0) return Array.Empty<byte>();
-        var buf = ReadBytesExact(r, count);
+        var buf = r.ReadBytes(count);
         if (buf.Length < count) throw new EndOfStreamException(
             $"Expected {count} bytes but stream contained only {buf.Length}.");
         return buf;