Switch UNIX socket paths to /run, and add a UNIX socket example for HAProxy

[villepeh]

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PR

Resolves #16698

Added a HAProxy UNIX socket example as well. It was one of the reasons I wanted to check if we should swap /var/run to /run, first. I've been using Synapse's UNIX sockets with HAProxy for a while now with no issues.

For consistency, I also reversed the order of the example worker configuration replication and client/federation fields as every other example configuration lists replication stuff first, and a public listener second.

Signed-off-by: Ville Petteri Huh villep8@gmail.com

[villepeh]

One more thing to note that I didn't feel like including into this PR as this one is mostly about the docs: If you add RuntimeDirectory=synapse to your matrix.service, systemd will automatically create /run/synapse for the Synapse user which can be used for storing the .sock files.

[DMRobertson]

Thank you!