Improve promscale dashboard

[paulfantom]

What this PR does / why we need it

This is adding a way to select datasource and namespace in promscale dashboard.

I am going to port that also upstream (to promscale repo), so our copier script will work just fine.

Which issue this PR fixes

(optional, in fixes #<issue number>(, fixes #<issue_number>, ...) format, will close that issue when PR gets merged)

• fixes #

Special notes for your reviewer

Checklist

• [x] Chart Version bumped
• [x] CLA signed

[paulfantom]

Oh, we need to do that in promscale first...

[paulfantom]

Promscale side is done.