[HPU] [Serve] [experimental] Add vllm HPU support in vllm example

[KepingYan]

Why are these changes needed?

This PR adds vllm HPU support in vllm example (https://github.com/ray-project/ray/pull/45430). The added codes will check whether the HPU device exists before allocating resources to vllm actors. If it exists, HPU resources are used, otherwise GPU resources are still used.

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Checks

• [ ] 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 :(