Closes #106565
When generating multiple certificates which all
share the same server + email, lego will attempt
to create an account multiple times. By adding an
account creation target certificates which share
an account will wait for one service (chosen at
config build time) to complete first.

systemd-tmpfiles is no longer required for
most of the critical paths in the module. The
only one that remains is the webroot
acme-challenge directory since there's no
other good place for this to live and forcing
users to do the right thing alone will only
create more issues.

Closes #106603
Some webservers (lighttpd) require that the
files they are serving are world readable. We
do our own chmods in the scripts anyway, and
lego has sensible permissions on its output
files, so this change is safe enough.

The instructions on recreating the cert were missing --what=state.
Also added a note on ensuring the group of manual certs is correct.

- Added an ExecPostStart to acme-$cert.service when webroot is defined to create the acme-challenge
directory and fix required permissions. Lego always tries to create .well-known and acme-challenge,
thus if any permissions in that tree are wrong it will crash and break cert renewal.
- acme-fixperms now configured with acme User and Group, however the script still runs as root. This
ensures the StateDirectories are owned by the acme user.
- Switched to list syntax for systemd options where multiple values are specified.

I found a logical error in the bash script, but during
debugging I enabled command echoing and realised it
would be a good idea to have it enabled all the time for
ease of bug reporting.

nixos/acme: Fixes for account creation and remove tmpfiles usage