Closes #2107
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This PR introduces a new folder `test/monitoring` which contains a
Docker Compose file that creates a Grafana and a Prometheus server
locally for the developer. It connects up with a localnet installation.

The localnet Docker compose file (`compose.yml`) was extended to allow
Prometheus traffic from the container and documentation was updated to
reflect the changes.

Short way to execute:
```
make build-linux localnet-start monitoring-start
```
---

The JSON files are pre-populated Grafana dashboards. Two of them are
from the qa-infra repository, one is part of host monitoring with
"node-explorer" and one is a new one created for storage experiments
that are currently ongoing.

#### PR checklist

- [ ] Tests written/updated - no Go code change
- [X] Changelog entry added in `.changelog` (we use
[unclog](https://github.com/informalsystems/unclog) to manage our
changelog)
- [X] Updated relevant documentation (`docs/` or `spec/`) and code
comments - test docs were updated
- [X] Title follows the [Conventional
Commits](https://www.conventionalcommits.org/en/v1.0.0/) spec

---------

Co-authored-by: Anton Kaliaev <anton.kalyaev@gmail.com>
(cherry picked from commit e8b4efa)