This also updates `docs/configuring-playbook-own-webserver.md`,
trying to make it up-to-date with all recent changes.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2480

Referenced here: 06f5be4fa5 (r100414988)

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2375

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2451

Related to 4c9f96722f

This helps large deployments which need to open up thousands of ports
(matrix_coturn_turn_udp_min_port, matrix_coturn_turn_udp_min_port)

On a test VM, opening 1k ports takes 17 seconds for Docker to "publish"
all of these ports (setting up forwarding rules with the firewall, etc),
so service startup and shutdown take a long amount of time.

If host-networking is used, there's no need to open any ports at all
and startup/shutdown can be quick.

Inspired by: https://www.rtcsec.com/article/cve-2020-26262-bypass-of-coturns-access-control-protection/

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2227

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2386

This role is usable on its own and it's not tied to Matrix, so
extracting it out into an independent role that we install via
ansible-galaxy makes sense.

This also fixes the confusion from the other day, where
`matrix_postgres_*` had to be renamed to `devture_postgres_*`
(unless it was about `matrix_postgres_backup_*`).
We now can safely say that ALL `matrix_postgres_*` variables need to be
renamed.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2305

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2090

Improves:

- https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/2232
- https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2217#issuecomment-1304366791

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.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2038

As stream writer workers are also powered by the `generic_worker`
Synapse app, this necessitated that we provide means for distinguishing
between them and regular `generic_workers`.

I've also taken the time to optimize nginx configuration generation
(more Jinja2 macro usage, less duplication).

Worker names have also changed.
Workers are now named sequentially like this:
- `matrix-synapse-worker-0-generic`
- `matrix-synapse-worker-1-stream-writer-typing`
- `matrix-synapse-worker-2-pusher`

instead of `matrix-synapse-worker_generic_worker-18111` (indexed with a
port number).

People who modify `matrix_synapse_workers_enabled_list` directly will
need to adjust their configuration.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2089

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2043

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2012

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2002

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1894

Improvement over e4caf3fa81.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1921

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1921

servers