[php-src] PR #25048: Fix GH-8832: Honor protocol_version for proxy CONNECT requests

Pull Request: https://github.com/php/php-src/pull/25048 Author: glbessa Closes GH-8832 The http stream wrapper always sends the CONNECT request used to tunnel HTTPS through a proxy as HTTP/1.0, regardless of the protocol_version context option. Proxies that only accept HTTP/1.1 (e.g. Envoy, as in the issue) answer with 426 Upgrade Required, making file_get_contents() over HTTPS through such a proxy impossible. This makes the CONNECT request honor the existing protocol_version context option, and sends the Host header (the target authority) that HTTP/1.1 requires: ``` CONNECT www.php.net:443 HTTP/1.1 Host: www.php.net:443 ``` When the option is not set, nothing changes: CONNECT is still sent as HTTP/1.0, without Host. Notes: - I reused protocol_version rather than adding a new option such as proxy_protocol_version, since users setting it most likely expect it to apply to the whole exchange, and it keeps the API surface unchanged. Happy to switch if a separate option is preferred. - Handling 426 Upgrade Required automatically (as discussed in the issue) does not help here, since the proxy in the report closes the connection and sends no Upgrade header. - The version is formatted exactly like the main request line (zval_get_double() + %.1F), so both lines always agree. - Added a test based on the existing http_proxy_ssl_connect_0x.phpt tests; the HTTP/1.0 default is already covered by http_proxy_ssl_connect_01.phpt. Added an UPGRADING entry under "Changed Functions". 🤖 Generated with [Claude Code](https://claude.com/claude-code)