[Torch FX] Add Data Free AWQ Conformance Test for Torch FX (#3622)

### Changes

Include Torch FX backend for data free AWQ weights compression test.

### Related tickets

169362

### Tests

Category | Job | Status | Job Number | Notes
-- | -- | -- | -- | --
GH WC | Weights Compression | Pass | <a
href="https://github.com/openvinotoolkit/nncf/actions/runs/16975099235">140</a>
|

Author: anzr299

tests/post_training/data/wc_reference_data.yaml

@@ -126,6 +126,10 @@ tinyllama_data_free_awq_backend_TORCH:
   metric_value: 0.85466
   num_int4: 94
   num_int8: 124
+tinyllama_data_free_awq_backend_FX_TORCH:
+  metric_value: 0.85466
+  num_int4: 94
+  num_int8: 124
 tinyllama_data_free_awq_backend_ONNX:
   metric_value: 0.8597
   num_int4: 230

tests/post_training/model_scope.py

@@ -578,8 +578,7 @@
                 awq_params=AdvancedAWQParameters(prefer_data_aware_scaling=False)
             ),
         },
-        # TODO: (andreyanufr) add torch.fx backend
-        "backends": [BackendType.OV, BackendType.TORCH, BackendType.ONNX],
+        "backends": [BackendType.OV, BackendType.TORCH, BackendType.FX_TORCH, BackendType.ONNX],
     },
 ]