Refactor support uploader to new FTP method

This refactors the --support-uploader option to use cURL to push the file to FTP.

I attempted to do this via net/ftp in ruby but the implementation there isn't great and the FTP server we use is strict on how it handles SSL connections and it rejects the connection resulting in a partial upload.

Requires as base64 encoded hash of a JSON object with the correct parameters:

echo '{"h":"IP_ADDRESS","u":"USERNAME","p":"PASSWORD"}' | base64

Customers can then run:

./gitlabsos.rb --support-uploader THE_HASH_HERE

and do everything in one step.

I've opened gitlab-com/support/support-team-meta#5437 (closed) to look in to adding the hash/an example to the internal note added by the bot on the ticket.