"ssl_ca" should not be required whenever TLS is enabled

[seanstory]

Bug Description

We have similar Rich Configurable Fields to enable SSL/TLS for a number of our connectors. If enabled, this often exposes several more configs, for example ssl_ca, which can be used to provide a root certificate authority that can authenticate the SSL certificate presented by the 3rd-party service.

However, these dependent SSL configs should not be required just because SSL is enabled.

To Reproduce

1. connect a MySQL connector
2. enable SSL for it
3. try to save configuration without specifying a certificate

Expected behavior

You should not need to specify a certificate to enable SSL