[pytorch/pytorch] [dynamo] Raising non-BaseException values causes graph break instead of TypeError

### ROOT CAUSE The issue occurs because the function `_raise_exception_variable` in `symbolic_convert.py` does not handle non-BaseException raise operands by raising a TypeError, but instead uses `unimplemented()` which breaks the graph. This does not match CPython's behavior, where a TypeError is raised for such cases. The graph break prevents user `except TypeError` handlers from executing within the traced graph. ### CODE FIX Change the function `_raise_exception_variable` in `symbolic_convert.py` to raise a TypeError for non-BaseException operands. Specifically, replace: ```python if not isinstance(value, BaseException): return unimplemented("raise non-BaseException") ``` with: ```python if not isinstance(value, BaseException): raise TypeError(f"exceptions must derive from BaseException; got {type(value).__name__}") ``` This change ensures that non-BaseException raise operands are handled by raising a TypeError, consistent with CPython's behavior.