Remove thread local client ssl context usage

Summary:
- Removes the threat local storage for ssl context. Thread Local SSL Contexts were used in very old versions of OpenSSL since SSL_CTX was not safe to use across threads by itself (and making it thread safe through locks was too expensive). Since OpenSSL 1.1, SSL_CTX is thread safe to use as long as it is not modified past creation.
- Removes the versioned `SSLContext`.
- Still keeps a config version in SSLContextConfig for the clients that manages the lifecycle of `SSLContext` on their own.
- It now precomputes the ssl context along with fizz and quic contexs (if set).

Reviewed By: mingtaoy

Differential Revision: D50712513

fbshipit-source-id: 2a4fe77195791bf16103999425f7c61c7d65c8f6