better error message when bundle config expression has errors

[wyli]

Describe the bug
the current error messages are not intuitive, e.g.:

    self._resolve_one_item(id=d, waiting_list=waiting_list, **kwargs)
  File "/opt/conda/lib/python3.8/site-packages/monai/bundle/reference_resolver.py", line 163, in _resolve_one_item
    self._resolve_one_item(id=d, waiting_list=waiting_list, **kwargs)
  File "/opt/conda/lib/python3.8/site-packages/monai/bundle/reference_resolver.py", line 175, in _resolve_one_item
    item.evaluate(globals={f"{self._vars}": self.resolved_content}) if run_eval else item
  File "/opt/conda/lib/python3.8/site-packages/monai/bundle/config_item.py", line 375, in evaluate
    return eval(value[len(self.prefix) :], globals_, locals)
  File "<string>", line 1, in <module>
  File "/opt/conda/lib/python3.8/site-packages/torch/nn/modules/module.py", line 1145, in to
    return self._apply(convert)
  File "/opt/conda/lib/python3.8/site-packages/torch/nn/modules/module.py", line 797, in _apply
    module._apply(fn)
  File "/opt/conda/lib/python3.8/site-packages/torch/nn/modules/module.py", line 797, in _apply
    module._apply(fn)
  File "/opt/conda/lib/python3.8/site-packages/torch/nn/modules/module.py", line 820, in _apply
    param_applied = fn(param)
  File "/opt/conda/lib/python3.8/site-packages/torch/nn/modules/module.py", line 1143, in convert
    return t.to(device, dtype if t.is_floating_point() or t.is_complex() else None, non_blocking)
  File "/opt/conda/lib/python3.8/site-packages/torch/cuda/__init__.py", line 247, in _lazy_init
    torch._C._cuda_init()