We've deprecated the old SSL URI options in favor of TLS options when implementing the unified URI options spec in CDRIVER-2869.

Let's consider deprecating use of the mongoc_ssl_opts_t struct as well for the same reason, in favor of having users pass TLS options through the URI. Note, since that struct is public, we cannot change field names or add new fields.

In addition, let's update all documentation examples that use mongoc_ssl_opts_t to use the URI options instead. E.g. http://mongoc.org/libmongoc/1.15.0/authentication.html#x-509-certificate-authentication