fix(proxyutil): enforce HTTP/1.1 ALPN and configure TLS dial context for HTTPS proxies

- Add `buildHTTPSProxyDialTLSContext` to handle HTTPS proxy TLS handshakes with configurable timeout and TLS options.
- Restrict ALPN `NextProtos` to HTTP/1.1 for HTTPS proxy connections to prevent HTTP/2 negotiation issues during proxy CONNECT tunneling.
- Support custom TLS configuration in `httpConnectDialer` for HTTPS proxy connections.

Closes: #5287