[ivalue] operator<<: don't error on invalid IValue tags (#112232)

While running the profiler, we observed a scenario where we observe IValues with invalid tags. Specifically, we try to convert the IValue to a string here:

https://github.com/pytorch/pytorch/blob/d3bf6803b62c79f1dafd1eec49b4bd65d5a27697/torch/csrc/profiler/util.cpp#L306-L308

and in the scenario with invalid IValues, an exception gets thrown here, in `operator<<`.

https://github.com/pytorch/pytorch/blob/d3bf6803b62c79f1dafd1eec49b4bd65d5a27697/aten/src/ATen/core/ivalue.cpp#L864

IMO, `<<` shouldn't error if the IValue is bad; instead, we should just print that the IValue tag is invalid.

Differential Revision: [D50760040](https://our.internmc.facebook.com/intern/diff/D50760040)
Pull Request resolved: #112232
Approved by: https://github.com/albanD

aten/src/ATen/core/ivalue.cpp

@@ -861,7 +861,7 @@ std::ostream& operator<<(std::ostream & out, const IValue & v) {
     }
 
   }
-  AT_ERROR("Tag not found: ", v.tagKind());
+  return out << "<Invalid IValue tag=" << std::to_string(static_cast<uint32_t>(v.tag)) << ">";
 }
 
 #undef TORCH_FORALL_TAGS