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.

Not doing {% if matrix_admin %} checks in the YAML also fixes some issues
with indentation being incorrect sometimes.

This should be backward compatible, except for mautrix-signal's case
where `matrix_mautrix_signal_bridge_permissions` previously existed
as a string, not a dictionary. `tasks/validate_config.yml` will catch
the problem an even provide a quick fix.

Reference: https://ansible-lint.readthedocs.io/en/latest/default_rules/#git-latest

Our variable naming is not necessarily consistent across roles.
I've tried to follow the naming conventions of each individual role.
All new variables are suffixed with `_version`, but the prefix may be
somewhat different.

This adds https://github.com/matrix-org/matrix-doc/pull/2409 to the
appservice registrations, enabling synapse to push EDUs to appservices.

Regression since f6097fbba1

Fixes a regression introduced in f6097fbba1fb, which was cauing Synapse
to die with this error message:

> ValueError: sender_localpart needs characters which are not URL encoded.

Fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/806

Fixes a problem like this:
> File "/usr/lib/python3.8/site-packages/mautrix/bridge/e2ee.py", line 79, in __init__
> raise RuntimeError("Unsupported database scheme")

mautrix-python's e2ee.py module expects to find `postgres://` instead of
`postgresql://`.

This makes the `sqlite://` URI match what we were using before
and what the config expects.

Looks like there are some that I missed in 087dbe4ddc

I was thinking that it makes sense to be more specific,
and using `_postgres_` also separated these variables
from the `_database_` variables that ended up in bridge configuration.

However, @jdreichmann makes a good point
(https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/740#discussion_r542281102)
that we don't need to be so specific and can allow for other engines (like MySQL) to use these variables.

Regression since 2d99ade72f and 9bf8ce878e94, respectively.

When SQLite is to be used, these bridges expect an `sqlite://`
connection string, and not a plain file name (path), like Appservice
Discord and mautrix-whatsapp do.

I don't use this bridge, so this is completely untested.

fixes matrix users unable to delete messages