disable multiplexing for some versions of curl

I'm behind a corporate proxy and was hitting a `Curl 2 (...) [CONN-1-0] send: no filter connected` error when trying to download some packages.

Some google research led me to rust-lang/cargo#12202 and its fix rust-lang/cargo#12234.

This PR backports this fix to composer.

> In certain versions of libcurl when proxy is in use with HTTP/2
multiplexing, connections will continue stacking up. This was
fixed in libcurl 8.0.0 in curl/curl@821f6e2

src/Composer/Util/Http/RequestProxy.php

@@ -22,6 +22,14 @@
  */
 class RequestProxy
 {
+    /**
+     * Known libcurl's broken versions when proxy is in use with HTTP/2
+     * multiplexing.
+     *
+     * @var list<non-empty-string>
+     */
+    private const BAD_MULTIPLEXING_CURL_VERSIONS = ['7.87.0', '7.88.0', '7.88.1'];
+
     /** @var ?contextOptions */
     private $contextOptions;
     /** @var ?non-empty-string */
@@ -101,6 +109,17 @@ public function getCurlOptions(array $sslOptions): array
             }
         }
 
+        /**
+         * Disable HTTP/2 multiplexing for some broken versions of libcurl.
+         *
+         * In certain versions of libcurl when proxy is in use with HTTP/2
+         * multiplexing, connections will continue stacking up. This was
+         * fixed in libcurl 8.0.0 in curl/curl@821f6e2a89de8aec1c7da3c0f381b92b2b801efc
+         */
+        if ($options[CURLOPT_PROXY] !== '' && ($version = curl_version()) !== false && in_array($version['version'], self::BAD_MULTIPLEXING_CURL_VERSIONS, true)) {
+            $options[CURLMOPT_PIPELINING] = /* CURLPIPE_NOTHING */ 0;
+        }
+
         return $options;
     }