Ignore constants in the legality error

[mgehre-amd]

This redirects the error message to talk about the actual problematic ops like cumsum.

[ljfitz]

Great! I remember you discussing/contributing something like this upstream already. Was that for torch-to-linalg?

[mgehre-amd]

Great! I remember you discussing/contributing something like this upstream already. Was that for torch-to-linalg?

The last thing I contributed was emitting an explicit "This operator is unsupported" error when we see a torch.operator { name = "torch.aten.cumsum"}