add priority and priorityClassName to ray-cluster template

[walterddr]

Why are these changes needed?

Similar to #181 we add priorityClassName and priority to the template

Related issue number

N/A

Checks

• [ ] I've made sure the tests are passing.
• Testing Strategy
  • [ ] Unit tests
  • [x] Manual tests
  • [ ] This PR is not tested :(

[walterddr]

manually tested but not sure if i did the right thing. @kevin85421 any suggestions on how to move forward? thanks

[kevin85421]

cc @MortalHappiness would you mind reviewing this PR? Thanks!

[MortalHappiness]

LGTM