Disabling the authentication for unix sockets makes it impossible to
use `rclone serve` behind a proxy that that communicates with rclone
via a unix socket.
Re-enabling the authentication should not have any effect on most
users of unix sockets as they do not set authentication up with a unix
socket anyway.
- 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