Add **kwargs to ViewMetrics.forward

Summary: GenericModel crashes in case the `aux` field of any Renderer is populated. This is because the `rendered.aux` is unpacked to  ViewMetrics.forward whose signature does not contain **kwargs. Hence, the contents of `aux` are unknown to forward's signature resulting in a crash.

Reviewed By: bottler

Differential Revision: D36166118

fbshipit-source-id: 906a067ea02a3648a69667422466451bc219ebf6

pytorch3d/implicitron/models/metrics.py

@@ -28,6 +28,7 @@ class ViewMetrics(torch.nn.Module):
         density_grid: Optional[torch.Tensor] = None,
         keys_prefix: str = "loss_",
         mask_renders_by_pred: bool = False,
+        **kwargs,
     ) -> Dict[str, torch.Tensor]:
         """
         Calculates various differentiable metrics useful for supervising