TS-2437: add a lifecycle hook to expose loaded SSL certificates to plugins

Add two new lifecycle hooks, TS_LIFECYCLE_SERVER_SSL_CTX_INITIALIZED_HOOK
and TS_LIFECYCLE_CLIENT_SSL_CTX_INITIALIZED_HOOK.

The reason for these hooks is that I have a use case to manipulate
(overwrite) the OpenSSL related callbacks in my plugin. I think it
is also useful for applications who have a need to change or retrieve
the SSL related attributes (callbacks, certs, configurations, etc).