Monitoring: installs Telegraf automatically on armv7l nodes

Details:
- Supports the installation of binary telegraf version A8 nodes in FIT/IoT-LAB platform.

- Uses the when clauses on ansible to distinguish the different architectures.
- Uses the default docker installation for: ansible_architecture != "armv7l".

- Huge refactor in installation process to use yml files for the different components: agent/collector/ui.
- The old version used priors to install python3/docker on hosts. However, we cannot use them in A8 nodes.
- The yml files add these dependencies only if architecture != "armv7l".

Obs.:
- Telegraf binary version is fixed to 1.17.0
(enoslib/service/monitoring/roles/agent/defaults/main.yml).