fix BigQueryInsertJobOperator's return value and openlineage extraction in deferrable mode

[kacpermuda]

This PR fixes two things:

1. Return value of BigQueryInsertJobOperator's execute_complete() (so execution in deferrable mode) will now be an actual BQ job id instead of None. As described in this docs, when deferring: No state will persist, such as local variables or attributes set on self., so assigning value to self.job_id within execute() had no effect and was not actually used in execute_complete().

2. We are re-assigning the job_id in execute_complete() as an instance attribute, so that we can later use it within OpenLineage method even when in deferrable mode. We are also re-creating any attributes (hook) that may be missing as a result of the state keeping logic mentioned above.

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[shahar1]

Could you please add some tests?

[kacpermuda]

Added some tests to check that we indeed re-assign the job_id from the event. @shahar1