HTTP/2 stream-dependency tree UAF

A use-after-free vulnerability exists in libcurl when an application configures an HTTP/2 stream-dependency tree via `CURLOPT_STREAM_DEPENDS` or `CURLOPT_STREAM_DEPENDS_E`, subsequently invokes `curl_easy_reset()`, and finally terminates the handle with `curl_easy_cleanup()`. During this final cleanup phase, libcurl attempts to access and modify an internal structure that was already freed during the reset operation.