Consolidate AWQ quantization into single awq_marlin.py file
Merge awq.py and awq_marlin.py into a single file, eliminating the
circular import between them. awq.py becomes a backward-compat shim.
Follows the same structure as gptq_marlin.py.
Co-authored-by: Claude
Signed-off-by: Robert Shaw <robertgshaw2@gmail.com>
