This paves the way for installing other roles into `roles/galaxy` using `ansible-galaxy`,
similar to how it's done in:

- https://github.com/spantaleev/gitea-docker-ansible-deploy
- https://github.com/spantaleev/nextcloud-docker-ansible-deploy

In the near future, we'll be removing a lot of the shared role code from here
and using upstream roles for it. Some of the core `matrix-*` roles have
already been extracted out into other reusable roles:

- https://github.com/devture/com.devture.ansible.role.postgres
- https://github.com/devture/com.devture.ansible.role.systemd_docker_base
- https://github.com/devture/com.devture.ansible.role.timesync
- https://github.com/devture/com.devture.ansible.role.vars_preserver
- https://github.com/devture/com.devture.ansible.role.playbook_runtime_messages
- https://github.com/devture/com.devture.ansible.role.playbook_help

We just need to migrate to those.

`frontend_proxy` workers have been superseded by `generic_worker` workers.
Related to https://github.com/matrix-org/synapse/pull/13645

Source: https://github.com/matrix-org/synapse/blob/v1.59.0/docs/upgrade.md#deprecation-of-the-synapseappappservice-and-synapseappuser_dir-worker-application-types

As an alternative, we should probably find a way to run one or a few
more generic workers (which will handle appservice and user_dir stuff) and
update `homeserver.yaml` so that it would point to the name of these workers using
`notify_appservices_from_worker` and `update_user_directory_from_worker` options.

For now, this solves the deprecation, so we can have a peace of mind
going forward.

We're force-setting these worker counts to 0, so that we can clean up
existing homeservers which use these worker types. In the future, these
options will either be removed or repurposed (so that they transparently
create more generic workers that handle user_dir/appservice loads).

These endpoints should not be proxied to a generic Synapse worker
without other preparation (setting up stream writers, sending traffic
to a specific stream writer, etc.).

Disabling them for now. In the future, we'd like to fix up our awk
script to disable them automatically.

This is a fix up for 058fedff91

This prevented us from keeping our workers reverse-proxying definitions
updated since Synapse v1.54.0.

The last `workers.md` file we could parse is at commit
02632b3504.
Parsing regressed at commit c56bfb08bc071368db23f3b1c593724eb4f205f0,
because the introduction message for `synapse.app.generic_worker` said
"If":

> If a worker is set up to handle a..

.. which made the AWK script think that definitions below were
conditional (which they're not in this case).

This patch fixes up the regex for determining if a line is conditional
or not, so that it doesn't trip up. Hopefully, it doesn't miss something
important.

1472958e25 reverted some of the v3 changes. I'm not sure why. Running the `workers-doc-to-yaml.sh` script now puts them back 🤷‍♂️.

We had to remove UID/GID environment variables that we used to pass
to the Synapse container, because it was causing a problem after
https://github.com/matrix-org/synapse/pull/11209

We were using both `--user` and UID/GID environment variables until now.

1f196f59cb

Related to:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1287
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1288

.. but does it in a more complete way

Should have been part of 9daeb39710