Added JOB_STATE_CANCELLED and pool_sleep GCP Dataflow Operators

[jcamatta]

Added an 'elif' block in the 'async def run(self)' method of 'TemplateJobStartTrigger', which captures 'JOB_STATE_CANCELLED'. This prevents the triggerer from looping indefinitely when a dataflow is cancelled. This also required updating the 'execute_complete' method of both 'DataflowStartFlexTemplateOperator' and 'DataflowTemplatedJobStartOperator', which now raise an 'AirflowException(event["message"])' when the job has the status "cancelled". So, if you cancel the job in the Google console, this will be reflected in the Airflow task execution.

Added 'pool_sleep' as an optional argument to the constructor of 'DataflowStartFlexTemplateOperator', preserving its default value of 10 seconds. This argument is passed to the 'TemplateJobStartTrigger' constructor when the 'self.defer' method is called in 'execute'.

Added tests to TemplateJobStartTrigger, DataflowStartFlexTemplateOperator and DataflowTemplatedJobStartOperator.

[boring-cyborg]

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[hussein-awala]

Could you please add a test for this change?

[jcamatta]

@hussein-awala done.

[eladkal]

I fixed some of the static checks and rebased.
@jcamatta there are additional static checks that requires fixing. Can you please handle it?

[jcamatta]

Hi, @eladkal . If you dont mind, I will try to take this in the weekend since right now i am full of work.

[github-actions]

This pull request has been automatically marked as stale because it has not had recent activity. It will be closed in 5 days if no further activity occurs. Thank you for your contributions.