Support "protocol_version" stream context option for proxy connections

Description

Hello. We have protocol_version option for talking with remote host using specified HTTP protocol version. However, HTTP connection to proxy always goes with HTTP/1.0 which upsets my proxy server.

Example:

<?php
$ctx = stream_context_create(
  ['http' => ['proxy' => 'tcp://corporate-proxy.example:3128']]
);
echo file_get_contents("https://getcomposer.org/versions", false, $ctx);

Result:

Warning: file_get_contents(): SSL: Connection reset by peer in a.php on line 5

Warning: file_get_contents(https://getcomposer.org/versions):
  Failed to open stream: Cannot connect to HTTPS server through proxy in a.php on line 5

Actual request as seen by wireshark:

CONNECT getcomposer.org:443 HTTP/1.0

HTTP/1.1 426 Upgrade Required
date: Mon, 20 Jun 2022 10:23:30 GMT
server: envoy
connection: close
content-length: 0

My proxy server supports only HTTP/1.1. So it's would be very handy to have an option for configuring http protocol version for proxy connections.

Start with PHP's HTTP stream wrapper and the proxy CONNECT request path, comparing them with existing protocol_version handling for direct requests. Verify that the option applies to proxy connections and exercise the HTTPS-through-proxy example, confirming the CONNECT request uses the configured HTTP version.