Node's address lookup strips the scope ID from link-local IPv6
addresses, making them invalid and unable to be connected to.

We're getting hit with this since Node 17 because it now defaults to the
`verbatim` dns-result-order and this happens to return the link-local
IPv6 address for `matrix.archlinux.org` first.

Specify `ipv4first` so we return to Node 16's behavior.

This was a regression which has been fixed upstream.

This reverts commit 67e7677e.

We're no longer allowed to reserve formerly used namespaces.

- Drop the custom service file, use the packaged one
- Merge in the comments from the packaged config file

The JournalHandler doesn't support flushing, anyway.

This one is pretty spammy with warnings that don't mean much.

Other caches around this code use 500000 entries, so just copy that.

This cache was seeing constant evictions at its former size (70k).

With a size of 200k it now stabilizes at ~122k entries with a
significant drop in server load.

Now that Pantalaimon refuses operations until it has sync'ed with the
homeserver, we need to give it time to do so or Mjolnir will refuse to
start.

!473