Evaluate extending OpenSSLCertificateOptions to set SSL_OP_CLEANSE_PLAINTEXT option

[evilaliv3]

SSL_OP_CLEANSE_PLAINTEXT is an option introduced starting from OpenSSL version 3 that enabled to configure the library to automatically securely clean buffers as soon that SSL_free is called.

I consider that enabling this option in the secure OpenSSLCertificateOption by default would be very rilevant to twisted and its end users.

Just a a very remote possibility we could make it possible to disable the configuration.

Reference:

• https://www.openssl.org/docs/manmaster/man3/SSL_CTX_clear_options.html
• Add SSL_OP_CLEANSE_PLAINTEXT to exported set of options pyca/pyopenssl#1302