Update PositionWeightedModule to make it jit trace compitable

Summary:
In
```
torch.ops.fbgemm.offsets_range(features[key].offsets().long(), torch.numel(features[key].values())
```
This part
```
torch.numel(features[key].values()
```

will be traced into constant

Reviewed By: snabelkabiya, houseroad

Differential Revision: D53744703

fbshipit-source-id: bf87eeaacf295b82b4591fb53029f66868ab8d86

torchrec/modules/feature_processor.py

@@ -40,6 +40,14 @@ def position_weighted_module_update_features(
     return features
 
 
+@torch.jit.script_if_tracing
+@torch.fx.wrap
+def offsets_to_range_traceble(
+    offsets: torch.Tensor, values: torch.Tensor
+) -> torch.Tensor:
+    return torch.ops.fbgemm.offsets_range(offsets.long(), torch.numel(values))
+
+
 # Will be deprecated soon, please use PositionWeightedProcessor, see full doc below
 class PositionWeightedModule(BaseFeatureProcessor):
     """
@@ -86,8 +94,8 @@ def forward(
 
         weighted_features: Dict[str, JaggedTensor] = {}
         for key, position_weight in self.position_weights.items():
-            seq = torch.ops.fbgemm.offsets_range(
-                features[key].offsets().long(), torch.numel(features[key].values())
+            seq = offsets_to_range_traceble(
+                features[key].offsets(), features[key].values()
             )
             weighted_features[key] = JaggedTensor(
                 values=features[key].values(),