Larger deployments may wish to run migration more often.

Signed-off-by: Joe Kappus <joe@wt.gd>

It's unnecessary when `pusher_instances` is populated.

Source: 6acb6d772a

It's unnecessary when `federation_sender_instances` is populated.

Source: 6acb6d772a

Synapse Worker configuration updates are coming later.

This path is accessed by the s3 storage provider stuff and needs to be
ensured.

Broken by 7c5c3aedc

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.

This allows people to augment the Synapse image with custom tools and
addons without having to rebuild it from scratch.

If customizations are enabled, the playbook will build a new
`localhost/matrixdotorg/synapse:VERSION-customized` image
on top of the default one (`FROM matrixdotorg/synapse:VERSION`)
and with custom Dockerfile build steps.

For servers that self-build the Synapse image, the Synapse image will be
built first, before proceding to extend it the same way.

In the future, we'll also have easy to enable Dockerfile build steps
for modules that the playbook supports.

In the future, we'll also inject media storage providers that we support
into the `matrix_synapse_media_storage_providers_auto` list.

If someone is using Dendrite and enabling Grafana, we'll no longer
download Synapse dashboards.

If someone is not using node-exporter, we'll no longer download node
exporter dashboards.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2133

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/2103

.. although.. manual configuration is discouraged in most cases.

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.

`frontend_proxy` workers have been superseded by `generic_worker` workers.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

This is done in anticipation of this option's removal in the
upcoming Synapse v1.66.0 release (likely tomorrow).

See: https://matrix-org.github.io/synapse/v1.66/upgrade.html#delegation-of-email-validation-no-longer-supported