Remove SslWrapper.toSSLSession

Filing this for myself, though I might not get to it just yet. The session refactor didn't quite remove the `SSL_SESSION`-based Java session object. We should be able to treat `SSL_SESSION` as largely opaque and avoid duplicating accessors between `SSL` and `SSL_SESSION`:

1. Use the ActiveSession as the session parameter to putSessionData. It's just being used as a session cache key.
2. Either make AbstractSSLSession.getSession never return anything like Netty or have it return an object with no properties at all. It's really not a useful function.
3. Fix the session format to remove the redundant copies of OCSP and SCT fields.