Serialize curl_multi_cleanup calls for OpenSSL <1.1.0

[clintonpi]

Motivation:

URLSession elusively crashes due to race conditions in OpenSSL <1.1.0 when calling curl_multi_cleanup concurrently on different threads.

Modifications:

• Add CFURLSessionSSLVersion CFURLSessionSSLVersionInfo(void) for detecting the OpenSSL version in use.
• Adjust _MultiHandle.deinit to use a process-wide lock to serialize curl_multi_cleanup calls for environments with OpenSSL <1.1.0.

Result:

Prevents the crash while avoiding unnecessary performance overhead for newer OpenSSL versions which are thread-safe.

Testing:

Passing existing tests is sufficient. However, without this patch, the code snippet below crashes about once in 20 runs on Amazon Linux 2

$ curl --version
curl 8.3.0 (aarch64-koji-linux-gnu) libcurl/8.3.0 OpenSSL/1.0.2k-fips zlib/1.2.7 libidn2/2.3.0 libpsl/0.21.5 (+libidn2/2.3.0) libssh2/1.4.3 nghttp2/1.41.0 OpenLDAP/2.4.44
Release-Date: 2023-09-13
...

DispatchQueue.concurrentPerform(iterations: 100) { _ in
    let session: URLSession = URLSession(configuration: URLSessionConfiguration.default)
    DispatchQueue.concurrentPerform(iterations: 100) { _ in
        _ = session
    }
}

[jrflat]

@swift-ci please test