Update Grafana (8.5.3 -> 9.0.1)

Update Prometheus (v2.33.3 -> v2.36.2)

This shall indicate that the public url of maubot is here configured the same as matrix_server_fqn_matrix but this must not be the case.
In the config I used the matrix fqnd directly as this part of the config is directly bound to the homeserver we want to connect to (but can not use the internal)

Added a note on managing the basic_auth password on external prometheus

The /data is hardcoded in the container

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

No functionality changed

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

Co-authored-by: Slavi Pantaleev <slavi@devture.com>

servers

> Error:   19:3      error    wrong indentation: expected 4 but found 2  (indentation)

Fixup for ba51997f7b

We redefine these variables in `group_vars/matrix_servers`, but it's better
to have some defaults in the role as well.

Use prebuilt ARM images for coturn / synapse-admin

* synapse-admin arm64 builds available since 2021-12-17 v.0.8.4 [awesometechnologies/synapse-admin:0.8.5](https://hub.docker.com/layers/synapse-admin/awesometechnologies/synapse-admin/0.8.5/images/sha256-eb54b8660c4641641b8acd08fd2dfc94ecc3fc604860f9e8b286a38008e3f3b6?context=explore)

* coturn arm32/arm64 builds available since 2021-04-15 v.4.5.2-r0-alpine [coturn/coturn:4.5.2-r12](https://hub.docker.com/layers/coturn/coturn/coturn/4.5.2-r12/images/sha256-94887581bb1093085033be0494c3a651bd40034afba1867ddc78b8ba32dc2faf?context=explore)

Update Buscarron 1.1.0 -> 1.2.0

Synapse workers should respect X-Forwarded headers

Currently, Synapse workers ignore the X-Forwarded headers, which leads to internal Docker IP addresses randomly appearing in the users' device list.

This adds the `x_forwarded: true` option to the worker config, fixing the issue.

Fixup for 5eff67371d - https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1884

add synapse media_retention