Expected to have regressed after https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/1008

This patch comes with its own downsides (as described in the comments
for matrix_prometheus_node_exporter_container_http_host_bind_port),
but at least there's:
- no security issue
- metrics remain readable from matrix-prometheus (even if the network metrics are inaccurate)

A better patch is certainly welcome.

This reverts commit d0cd709c08.

This reverts commit 68ca81c8c2.

- duplicate X-Content-Type-Options
- X-Frame-Options header
- Referrer-Policy [Might consider adding variable]
- Secure flag with cookies
- matrix_grafana_content_security_policy variable for [Content Security Policy](https://grafana.com/docs/grafana/latest/administration/configuration/#content_security_policy)

Latest stable grafana version is [7.5.4 (2021-04-14)](https://github.com/grafana/grafana/releases/tag/v7.5.4)

Supposedly fixes https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/907

X-XSS-Protection: 1; mode=block; header, for basic XSS protection in legacy browsers.
X-Content-Type-Options: nosniff header, to disable MIME sniffing

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/999

These old versions of TLS rely on MD5 and SHA-1, both now broken, and contain other flaws. TLS 1.0 is no longer PCI-DSS compliant and the TLS working group has adopted a document to deprecate TLS 1.0 and TLS 1.1.

Signed-off-by: Ahmad Haghighi <haghighi@fedoraproject.org>

fix nginx boot loop

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/868

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/868

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/868

.. and prevent variable name overlap with `matrix-postgres` for the
other variables as well.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/868

See these last commits:

tulir/mautrix-signal@4fc34330c1f6947aece67863b0d04da34c776f80

tulir/mautrix-signal@64bc5c36a509ba435a0b01cf44afb1b5d2642efd

tulir/mautrix-signal@ddda1666d41d28750cc59d070e4388b24add6ad9

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/pull/963

This also simplifies Prerequisites, which is great.

It'd be nice if we were doing these checks in some optional manner
and reporting them as helpful messages (using
`matrix_playbook_runtime_results`), but that's more complicated.
I'd rather drop these checks completely.

Related to https://github.com/spantaleev/matrix-docker-ansible-deploy/issues/970