SslContext creation caching

SSL setup is rebuilt on every connection, and this is very costly when creating SSL connection.
Loading the trust store and key store (parsing PEM/PKCS12 and building the trust/key managers) is the costly part of opening an SSL connection, and it is repeated for each new SSL connection.
Goal is to cache the parsed trust and key managers and reuse them across connections, SSL socket factory will still be created fresh per connection on purpose, so no TLS session is shared between connections (no resumptions).

(cache key includes the SSL configuration plus a trust file check (last-modified + size), so replacing a store file on disk remove cache).