Remove the distinction between "hidden" and removed transports

[Hocuri]

Right now, when clicking on "Remove" for a transport in the UI, there are the options to either hide or actually remove it. We would like to get rid of this distinction. In order to do this:

• In the UI, there will only be a button "Remove", not "Hide".
• When a user clicks "Remove", then the relay becomes unpublished.
• Unpublished relays are only queried every day (or every hour), similar to the removed scan_folders feature, in order not to waste energy on them.
• If no message arrived to an unpublished relay in 50 days, then it is permanently removed.
  • The exact time here needs to be determined.
  • We might build something smarter here like "If no message arrived to an unpublished relay in 50 days, but messages did arrive to the other relays"

@r10s did I accurately describe the outcome of our discussion? I wanted to write it down before we forget it.
cc @link2xt

[r10s]

the final deletion determination needs to be figured out, otherwise, yes.

gist of that change is:

• simplify ui
• remove a footgun. advanced or not, we already now have reports of ppl get disconnected from the network by doing things wrong
• pave the path for automatic relay management, so replacing a no longer functional relay is mostly riskless

idea on the horizon is that one onboards on the "relay network" which then works almost automatically. reminder: delta chat is for the many, we are nerds, but we do not want to create a tool for nerds

[iequidoo]

• If no message arrived to an unpublished relay in 50 days, then it is permanently removed.

At least blocked and contact request chats should be excluded here to avoid spammers from keeping an unpublished relay not removed

[link2xt]

Closing this in favor of more concrete issue #8384

I dropped "scan_folders"-like suggestion (it's cheap to keep IMAP connections, no need to add complexity with periodic "scanning") and added more details on the implementation and API.