Rename "ssl" to "tls", connect to IRC servers with TLS and port 6697 by default

[flashcode]

Feature description

Options, commands and documentation must be updated to use "TLS" instead of "SSL".
Connection to IRC servers must be with TLS and port 6697 by default.

Specification: https://specs.weechat.org/specs/2023-004-tls-options-and-connections.html