Rework metrics

[etienne-napoleone]

If we remove the metrics from TomoMaster, it would be really easy to migrate and it offers so much more insights.

[etienne-napoleone]

Might need #130 as netdata is better installed on the host os directly

[etienne-napoleone]

Starting by one master + n slaves where n is the number of machines
https://docs.netdata.cloud/streaming/#netdata-without-a-database-or-web-api-headless-collector
If later we need persistance, add https://docs.netdata.cloud/backends/

[etienne-napoleone]

Will be implemented gradually at the same time as infrastructure as code (#130)

[etienne-napoleone]

implemented in terraform devnet

[etienne-napoleone]

Have to fix #144