[New Feature][Habana-Main] speculative_decoding HPU support

[xuechendi]

Req - https://jira.habana-labs.com/browse/REQ-289 => target for 1.19

TODO:

• There remains one hardcode to HPUWorker, need to remove

Next Steps:

• 1. submit necessary codes change to vllm-upstream branch => WIP
• 2. support all 3 draft_model_types - mlp_speculator, medusa and others

FILL IN THE PR DESCRIPTION HERE

FIX #xxxx (link existing issues this PR will resolve)

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[xuechendi]

Run test with

python examples/offline_inference_spec_decode.py

[xuechendi]

@michalkuligowski , I fixed all comments, some suggestion might not work with existing codes, so I add explanation in the review

[xuechendi]

@michalkuligowski , may you help to trigger the CI again, I fixed yapf detected format issues.

[xuechendi]

@michalkuligowski , I updated the codes according to your last comments. For the draft_model_runner.py importing behavior change issue you mentioned in last comment, since draft_model_runner will be imported by spec_decode_runner and multi_step_decode_runner, we need to prevent the unnecessary importing error termination due to Cuda and ROCm flashattn support.
Since you think the previous fixing by simply changing raise to print is not very good, I provided an alternative fixing in latest commit.

After this PR merged, I will move on to the complete draft model support for medusa and mlp, and I'll revisit this draft_model_runner.py for better support.