Update vectorim/element-web Docker tag to v1.11.55

Hookshot wants a trailing slash for this route.

If we let Hookshot redirect, it goes to `/widgetapi/v1/static/`,
instead of `/hookshot/widgetapi/v1/static/`, so we take this matter into our
own hands.

Public URLs are like: `/hookshot/widgetapi/v1/static/`
.. which get translated to requests for: `/widgetapi/v1/static/`

Previously, we were stripping the whole `/hookshot/widgetapi` prefix,
which is wrong.

Some of these variables were ending up configuring services to expect
certificates.. yet there's no way they could get them.

fix ProxyPass directive by adding mandatory trailing slash

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/3114

Most of these files were defining a service, usually toward the end.
These lines have been moved upward.

Some components (mautrix-signal, mautrix-gmessages, etc.) were defining
a service conditionally (only if metrics are exposed, etc). This was
causing issues like these in the Traefik logs:

> level=error msg="service \"matrix-mautrix-twitter\" error: port is missing" providerName=docker container=matrix-mautrix-twitter-..

This changes the behavior of
`matrix_playbook_migration_matrix_nginx_proxy_uninstallation_enabled`
and is against what we initially described in the changelog entry,
but I've discovered some problems when the `matrix-nginx-proxy` service
and container remain running. They need to go.

This allows people to not include the `matrix-conduit` or
`matrix-dendrite` roles in their custom playbook (based on our roles)
and still not have the playbook choke on variables from these roles
missing.

For getting rid of the `matrix-synapse` role in a similar way,
more work is likely necessary.

After some checking, it seems like there's `/_synapse/client/oidc`,
but no such thing as `/_synapse/oidc`.

I'm not sure why we've been reverse-proxying these paths for so long
(even in as far back as the `matrix-nginx-proxy` days), but it's time we
put a stop to it.

The OIDC docs have been simplified. There's no need to ask people to
expose the useless `/_synapse/oidc` endpoint. OIDC requires
`/_synapse/client/oidc` and `/_synapse/client` is exposed by default
already.

10 seconds is a better default for slower (or overloaded) servers

Traefik also serves an internal entrypoint that all addon services
(bridges, bots, etc.) depend on, so it makes sense to have it be
available early on. It is injected as a systemd `required` dependency
for all services, so it would have been pulled earlier anyway (despite
the priority). Nevertheless, it's better to make the playbook-defined
priotities for services match, so that services are explicitly asked to
start in a more correct order.

With these changes in place now, all "start service" tasks executed by
Ansible cause a "change", indicating that all these services are started
in the correct order and none of them is unintentionally started as a
dependency for another.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3102

We likely weren't handling the `matrix_playbook_reverse_proxy_type: other-traefik-container`
case well before. Now, we should be.

Issues and Pull Requests were not migrated to the new
organization/repository, so `matrix-org/synapse/pull` and
`matrix-org/synapse/issues` references were kept as-is.

`matrix-org/synapse-s3-storage-provider` references were also kept,
as that module still continues living under the `matrix-org` organization.

This patch mainly aims to change documentation-related things, not actual
usage in full yet. For polish that, another more comprehensive patch is coming later.

Supersedes https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/3110

Update broken links in reverse proxies docs

Update dock.mau.dev/mautrix/discord Docker tag to v0.6.5

Update dock.mau.dev/mautrix/gmessages Docker tag to v0.2.4

Updated Grafana dashboard for MMR

Update vectorim/element-web Docker tag to v1.11.54