Update Elastic Stack chart to 2.0.0 to support kubernetes 1.16

What does this MR do?

Issue: #212255 (closed)

An upstream PR was necessary to fix our Elastic Stack configuration on Kubernetes 1.16. https://github.com/helm/charts/pull/21640

This MR uses the newly released chart. Since it includes an update from filebeat 6 to 7, a number of things are necessary:

• indices created by filebeat 6 are not compatible with indices created by filebeat 7. Most noteably the offset field is renamed to log.offset. This means we can't query old data after the upgrade. I updated the curator configuration to clean up those indices explicitely.
• The new filebeat chart includes an update to the kubernetes labels. Since those fields are immutable, we first need to delete the old filebeat resources before upgrading. For this I added a preinstall script that replays the same install command with --set filebeat.enabled=false.

Please note that this chart is deprecated and will be replaced in 13.0 #212564 (closed) so I'm looking for a quick fix and to avoid major changes in 12.10, please keep it in mind in your review 🙂

Screenshots

Does this MR meet the acceptance criteria?

Conformity

• Changelog entry
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