Before this change only serve http was Shutting down its server which
was causing other servers such as serve restic to leave behind their
unix sockets.
This change moves the finalisation to lib/http so all servers have it
and removes it from serve http.
Fixes#6648
- add support for unix sockets (which skip the auth).
- add support for multiple listeners
- collapse unnecessary internal structure of lib/http so it can all be
imported together
- moves files in sub directories of lib/http into the main lib/http
directory and reworks the code that uses them.
See: https://forum.rclone.org/t/wip-rc-rcd-over-unix-socket/33619Fixes: #6605
