Add Kubernetes Priority Classes support

[diego-ojeda-binbash]

What this PR does / why we need it:

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

[Place an '[x]' (no spaces) in all applicable fields. Please remove unrelated fields.

• [x] Chart Version bumped
• [ ] e2e tests pass
• [ ] Variables are documented in the README.md
• [ ] NEWS.md updated