[Chore] Use new golangci-lint rules only for ray-operator

[MortalHappiness]

Why are these changes needed?

Some CI fails because other modules (e.g. experimental) also use golangci-lint and the new rules in the repository root cause them to fail.

• https://github.com/ray-project/kuberay/actions/runs/9068220792/job/24915020733?pr=2141
• https://github.com/ray-project/kuberay/actions/runs/9093023649/job/24991053965?pr=2144

Therefore, this PR moves the .golangci.yml into the ray-operator folder.

Related issue number

N/A

Checks

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