[Release] Introduce --batch-size-to-kill to release chaos test framework

[jjyao]

Why are these changes needed?

Currently the chao test framework only kills one node at a time but that's not stressful enough to uncover some bugs. This PR introduces --batch-size-to-kill to allow multiple nodes being killed at the same time.

Related issue number

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• I've signed off every commit(by using the -s flag, i.e., git commit -s) in this PR.
• I've run scripts/format.sh to lint the changes in this PR.
• I've included any doc changes needed for https://docs.ray.io/en/master/.
  • I've added any new APIs to the API Reference. For example, if I added a
    method in Tune, I've added it in doc/source/tune/api/ under the
    corresponding .rst file.
• I've made sure the tests are passing. Note that there might be a few flaky tests, see the recent failures at https://flakey-tests.ray.io/
• Testing Strategy
  • Unit tests
  • Release tests
  • This PR is not tested :(

[jjyao]

batch_inference_chaos release test succeeded: https://buildkite.com/ray-project/release/builds/27890#0193b7fe-1114-4f40-ad8a-2f0f32af2147

Total chaos killed: {'79e3395993aa90570e383b9169e7d88cd2f5f020e90f6dae3c125e02', '56e5b40eee84b3a7b894d5817fcc0387bb77640deff5149ea5565627', 'd3f85384b2f036dee72798baf31ac894abaa810707cc56675e03f611', '66804584692eccb2e6b9ac9762c5f8e3735e363fca4f38bf08777fb9', '1018025a3232d3b7794ffd96a8566ad734538bbf15c9d2dfa440ca48', 'bacb1b33e6a3294838436ef9bfe89ad0710862d7457adda896ef6381'}