Create helm chart for metrics-operator

[mowies]

Goal

Set up a standalone Helm chart for the metrics operator taking what is currently in the main KLT chart and moving it into a separate chart.

Details

• the helm chart should live under metrics-operator/chart
• the metrics-operator relevant helm values should be moved over to the new chart
• CRDs that are specific to the metrics-operator should be moved to the new chart and removed from the old chart
• change the default kubernetes labels so that they make more sense in the umbrella/subchart context
• change the container names to something better than manager
• adapt the integration test keptn install action to make sure that everything still works

DoD

• new chart is created
• new chart can be installed standalone and can work together with an existing KLT chart without the metrics-operator

Notes

Some inspiration can be taken from the initial PoC for the umbrella chart here, but that still works with helmify.