Add full WSS support to public server list (using wss_port, overriding
insecure port), favorite servers list, and direct connections, and show
which servers are secure.

Revert the upstream's removal of `legacy` ServerInfo field, as I use it
to filter out legacy servers. To differentiate schemes, the `scheme`
field is used, either "ws" or "wss". I don't see the reason to add "tcp"
protocol when we don't even support it.

For the UI, add icons for secure and insecure connections. Highlight
secure servers with a green background.

In the favorite server dialog, a checkbox was added to select whether
the server is using WSS.

In the direct connection dialog, support "wss" scheme and default ports:
80 for WS, 443 for WSS, as per the WebSocket specification.