test(e2e): add utls dialer regression suite (#888)

Adds an e2e suite (tests/e2e/utls_test.go + testdata/utls/*)
that exercises the utls dialer in a forward-proxy chain:

  curl -> client gost (http proxy :8080)
       -> chain node (http connector + utls dialer)
         -> server gost (http over TLS listener :8443)
           -> tcp-echo

Two cases:

- TestUTLSInsecure: regression for go-gost/gost#887. A utls
  dialer with `secure: false` must still complete the handshake
  (InsecureSkipVerify must be honoured). The old unsafe cast read
  garbage for InsecureSkipVerify and the handshake failed.
- TestUTLSSecureWithCA: exercises the converter's RootCAs /
  ServerName path with a CA-signed server cert.

Uses the deterministic `Chrome` fingerprint (not `randomized`, which
randomises the ClientHello and is flaky against a standard Go TLS
server).

Bumps github.com/go-gost/x to v0.13.11, which fixes the
second half of #887: the curve-preference enum divergence between
crypto/tls and utls (Go 1.24+ appends PQC hybrid curves that
utls does not define).

Related: go-gost/gost#887, go-gost/x#111, go-gost/x#112

tests/e2e/testdata/utls/client_secure.yaml

@@ -0,0 +1,26 @@
+services:
+- name: http-proxy
+  addr: :8080
+  handler:
+    type: http
+    chain: utls-chain
+  listener:
+    type: tcp
+
+chains:
+- name: utls-chain
+  hops:
+  - name: hop-0
+    nodes:
+    - name: node-0
+      addr: {{.ServerAddr}}
+      connector:
+        type: http
+      dialer:
+        type: utls
+        metadata:
+          fingerprint: Chrome
+        tls:
+          secure: true
+          serverName: utls-server
+          caFile: /certs/ca.pem