[RayJob] Add Tests for Atomic Suspend Operation

[Yicheng-Lu-llll]

Why are these changes needed?

This PR adds tests for the atomic suspend operation. See #1799 and #1798 for more details.

Besides the new test, this PR also refactors the normal suspending test in rayjob_controller_suspended_test.go to make it more compact and compatible with the latest RayJob.

Related issue number

Closes #1799

Checks

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