Fix exception sampling logic

[damccorm]

Right now, PreCommit Python is persistently red - https://github.com/apache/beam/actions/workflows/beam_PreCommit_Python.yml?query=event%3Aschedule

When this goes red, we see the following errors:

Traceback (most recent call last): |  
  | File "apache_beam/runners/common.py", line 1501, in apache_beam.runners.common.DoFnRunner.process |  
  | return self.do_fn_invoker.invoke_process(windowed_value) |  
  | File "apache_beam/runners/common.py", line 689, in apache_beam.runners.common.SimpleInvoker.invoke_process |  
  | self.output_handler.handle_process_outputs( |  
  | File "apache_beam/runners/common.py", line 1687, in apache_beam.runners.common._OutputHandler.handle_process_outputs |  
  | self._write_value_to_tag(tag, windowed_value, watermark_estimator) |  
  | File "apache_beam/runners/common.py", line 1800, in apache_beam.runners.common._OutputHandler._write_value_to_tag |  
  | self.main_receivers.receive(windowed_value) |  
  | File "apache_beam/runners/worker/operations.py", line 263, in apache_beam.runners.worker.operations.SingletonElementConsumerSet.receive |  
  | self.consumer.process(windowed_value) |  
  | File "apache_beam/runners/worker/operations.py", line 950, in apache_beam.runners.worker.operations.DoOperation.process |  
  | with self.scoped_process_state: |  
  | File "apache_beam/runners/worker/operations.py", line 951, in apache_beam.runners.worker.operations.DoOperation.process |  
  | delayed_applications = self.dofn_runner.process(o) |  
  | File "apache_beam/runners/common.py", line 1503, in apache_beam.runners.common.DoFnRunner.process |  
  | self._reraise_augmented(exn, windowed_value) |  
  | File "apache_beam/runners/common.py", line 1611, in apache_beam.runners.common.DoFnRunner._reraise_augmented |  
  | self._maybe_sample_exception(exc_info, windowed_value) |  
  | TypeError: Argument 'exn' has incorrect type (expected BaseException, got tuple) |  

This is because we pass sys.exc_info(), which returns a tuple, into a class expecting just the exception. This fixes that problem (though not the PreCommit yet)

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[damccorm]

Merging despite failing checks because this has sent a bunch of checks green and has reduced the number of failing tests for precommit python