Use only Helm docs plus other misc fixes

The main goal of this change is to make sure that there's only one source of truth for the documentation of the values, instead of having values.yaml and docs/values.md playing in different leagues. For this I'm switching the documentation tooling to use helm-docs.

The patchset also includes the following:

• Fix typos and some wording.
• Make sure that the scrapping interval options for the Kube and Node exporters are actually honored (values themselves kept)
• Remove logs' scrapping interval as I think it's a c&p artifact.
• Finish the job started by c40c0044 by adding an extra missing CI rule for the helm_lint job.