[Misc][UI] Allow using --kv-cache-dtype kebab-case flag

[simondanielsson]

Motivation

Currently you need to use the somewhat unconventional case --kv_cache_dtype, while every other argument in ATOM is kebab case.

Keep the old one for backwards compatibility.

Note: in the docs there are still lots of uses of the old version. Let's see when/if we want to rename those as well.

Technical Details

N/A

Test Plan

pytest tests/test_arg_utils_spec.py

Test Result

...
tests/test_arg_utils_spec.py .......                                                                                                                                      [100%]

=============================================================================== 7 passed in 0.03s ===============================================================================

Submission Checklist

• Look over the contributing guidelines at https://github.com/ROCm/ROCm/blob/develop/CONTRIBUTING.md#pull-requests.

[simondanielsson]

@ZhangLirong-amd Could I please request a review on this PR? Thanks

[github-actions]

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