chore: bump x to v0.15.1, add e2e tests for chainGroup and sniffing

- Bump github.com/go-gost/x v0.15.0 → v0.15.1
- ChainGroupSuite: matcher routing by host, probe dead-chain pre-marking
- SniffingSuite: SOCKS5+HTTPS w/o SNI, debug-only log on empty SNI
- Add RunHTTPSEchoContainer and https_echo.py test helper

tests/e2e/scripts/https_echo.py

@@ -0,0 +1,42 @@
+#!/usr/bin/env python3
+import os
+import subprocess
+import ssl
+from http.server import BaseHTTPRequestHandler, HTTPServer
+
+PORT = int(os.environ.get("PORT", "8443"))
+
+cert_dir = "/tmp/certs"
+os.makedirs(cert_dir, exist_ok=True)
+cert_file = os.path.join(cert_dir, "cert.pem")
+key_file = os.path.join(cert_dir, "key.pem")
+
+if not os.path.exists(cert_file) or not os.path.exists(key_file):
+    subprocess.run(
+        [
+            "openssl", "req", "-x509", "-newkey", "rsa:2048",
+            "-keyout", key_file, "-out", cert_file,
+            "-days", "365", "-nodes",
+            "-subj", "/CN=localhost",
+        ],
+        check=True,
+    )
+
+
+class Handler(BaseHTTPRequestHandler):
+    def do_GET(self):
+        body = b"hello-gost"
+        self.send_response(200)
+        self.send_header("Content-Length", str(len(body)))
+        self.end_headers()
+        self.wfile.write(body)
+
+    def log_message(self, format, *args):
+        return
+
+
+server = HTTPServer(("0.0.0.0", PORT), Handler)
+ctx = ssl.SSLContext(ssl.PROTOCOL_TLS_SERVER)
+ctx.load_cert_chain(cert_file, key_file)
+server.socket = ctx.wrap_socket(server.socket, server_side=True)
+server.serve_forever()