SSL support in routine load with kafka

[morningman]

Some Kafka cluster enables the encryption and authentication with SSL, which need client to offer certification file or client public/private key files when connecting to the Kafka brokers.

So we should allow user to specify their own files when creating routine load jobs.

I'm going to implement a Small File Manager in Doris, which allow user to upload some small files and save them in Doris. And user can later use or cite these files where and whenever they want.