feat: display TLS certificate checks configuration in connectivity view

[link2xt]

Screenshot:

[link2xt]

We should also warn about plaintext configurations because if plaintext connection is used then strict TLS certificate checks do not help. Have not decided where to put it yet, should probably be a red item at the top of "Incoming Messages" and "Outgoing Messages" if IMAP or SMTP configuration using plaintext connection is detected.

I also thought about adding proxy information to connectivity view, but this better goes to another screen where user can also change the settings: deltachat/deltachat-android#3276