[DO NOT MERGE] Refactor/aiter integration

[vllmellm]

Purpose

Test Plan

Test Result

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Essential Elements of an Effective PR Description Checklist

• The purpose of the PR, such as "Fix some issue (link existing issues this PR will resolve)".
• The test plan, such as providing test command.
• The test results, such as pasting the results comparison before and after, or e2e results
• (Optional) The necessary documentation update, such as updating supported_models.md and examples for a new model.
• (Optional) Release notes update. If your change is user facing, please update the release notes draft in the Google Doc.

[github-actions]

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[vllmellm]

Check if fp8_linear is initialised.

[vllmellm]

Add https://github.com/ROCm/vllm/blob/c88d6d2ec7299605bb2ed8a4aee9260d90ef0631/vllm/model_executor/layers/quantization/compressed_tensors/schemes/compressed_tensors_w8a8_fp8.py#L153 to the rocm_aiter_ops and use that to replace this if conditions.