Cleanup middleware logic

* Http2Connection now sets up the streams and returns a responseStream

tests/Connection/Http2ConnectionTest.php

@@ -0,0 +1,11 @@
+<?php
+
+namespace NoccyLabs\React\Http2\Connection;
+
+use PHPUnit\Framework\Attributes\CoversClass;
+
+#[CoversClass(Http2Connection::class)]
+class Http2ConnectionTest extends \PHPUnit\Framework\TestCase
+{
+
+}