feat(vector): Add option to use KEDA autoscaler

[artmakh]

Motivation KEDA provides possibility to scale pods based on any metric (or query) available in prometheus or many overs datasources. Since vector have wide variety of internal metrics better suitable for scaling decisions, it's nice to have possibility to choose KEDA instead of plain HPA

Approach How does this change address the problem?

It adds necessary values to helm chart and KEDA ScaledObject template

[spencergilbert]

Thanks for the contribution! I'll try and get a review on this early next week.

[spencergilbert]

Sorry - this is still on my radar, just been trying to finish up tasks from the last quarter.

[spencergilbert]

Closing due to inactivity