feat(ops/meta01): deploy irccat

This deploys irccat, connected to the #snix channel.

We drop the custom irccat third_party, it's 2 years older than the
latest version in nixpkgs.

The irccat.nix module file contains some of the code present in the TVL
version, it however moves the secrets merging to ExecStartPre=,
given https://github.com/systemd/systemd/issues/19604#issuecomment-989279884
has been fixed for almost a year.

Contrary to the setup there, we don't let irccat connect to ZNC, but
hackint directly (so make use of the secrets logic).

We also drop the network-online.target, and make this overall more
tolerant by using Restart=on-failure.

Change-Id: Ieac3b744b7ea58b8dddf1cdc37a8bc057b205b1b
Reviewed-on: https://cl.snix.dev/c/snix/+/30504
Autosubmit: Florian Klink <flokli@flokli.de>
Reviewed-by: Ryan Lahfa <ryan@lahfa.xyz>
Tested-by: besadii

ops/secrets/irccat-secrets.age

@@ -0,0 +1,11 @@
+age-encryption.org/v1
+-> ssh-ed25519 +qVung 3O7R2kPSWKYtSj2UtPdLihY0DTkoy0Cdjmk/mp2YTgA
+Z3ySYVXGzKy7EbIl1KKjPvcWE+Gr+YrDxQjSWhtjnOQ
+-> X25519 Z0zakQU8dXGTFghkdRFOBJ/lHZenShAxNyM+Vf8ccjs
+kggGzVfLrdfS21RTQPMQESf7h0UNGpHwLj0MhLf11qw
+-> ssh-ed25519 C2zWnA Byg3pvqGgZWgmbpnhsziFDzndMM6p0pd/Emsw+1NoTI
+PCPzVeD8iImOAJ/bP6x/LYKQA9iWT42efWWAZsGl7xg
+-> ssh-ed25519 LzO4tw yIkoQYky8Er+lodlBUUE0BYd4VfMdGKIHlVIaXTQPio
+XlS7JQp+yZP0qgZV0e1YIjF4KcQ/LZE5Za6CAB/gZOo
+--- mDqJdL1X9lyrrsjW0nYRbW13UN+xPDzW8j1rMp7PDBg
+`¼¿5‡s<08>r’‡?êÒ’s>Ä°$ßç¦e³Ê¨weX˜5j›_ÏÆñLR]RÑkÓ˜WÑž*ô?ÇË{³‡À«B#O^æ›e×Q…fĨbÅiäÖ"~yÞèéÑ