[php-src] PR #24323: ext/curl: Guard curl_reset(), copy and clone of a denied pushed handle

Pull Request: https://github.com/php/php-src/pull/24323 Author: iliaal Depends on #23850 and is stacked on its branch, so the first commit here is that PR's; only the second commit is new. When a CURLMOPT_PUSHFUNCTION callback keeps the pushed handle and denies the push, libcurl frees the easy handle and the CurlHandle is left with a NULL ch->cp. curl_reset(), curl_copy_handle() and clone pass that NULL to curl_easy_reset() and curl_easy_duphandle() and segfault. This predates #23850 (reproduced on 57140099605); the other CurlHandle entry points already fail cleanly without an easy handle. The test depends on the dtor change in #23850: without it the kept handle's handlers leak and a debug build reports it. Not included: curl_getinfo() with CURLINFO_CERTINFO leaks the array it initialised when curl_easy_getinfo() fails, reachable through the same kept handle. That is a separate fix.