fix(ingest): use prev.ignored arg in DataProcessInstance

The high-level method DataProcessInstance.emit_process_end() actually ignores  start_timestamp_millis, which can be passed further to calculate durationMillis instead of using None.
This change makes emitter use this argument and save durationMillis.

metadata-ingestion/src/datahub/api/entities/dataprocess/dataprocess_instance.py

@@ -176,6 +176,8 @@ def end_event_mcp(
  :param result: (InstanceRunResult) the result of the run
  :param result_type: (string) It identifies the system where the native result comes from like Airflow, Azkaban
  :param attempt: (int) the attempt number of this execution
+ :param start_timestamp_millis: (Optional[int]) the start time of the execution in milliseconds
+
  """
  mcp = MetadataChangeProposalWrapper(
  entityUrn=str(self.urn),
@@ -215,12 +217,15 @@ def emit_process_end(
  :param result_type: (string) It identifies the system where the native result comes from like Airflow, Azkaban
  :param attempt: (int) the attempt number of this execution
  :param callback: (Optional[Callable[[Exception, str], None]]) the callback method for KafkaEmitter if it is used
+ :param start_timestamp_millis: (Optional[int]) the start time of the execution in milliseconds
+
  """
  for mcp in self.end_event_mcp(
  end_timestamp_millis=end_timestamp_millis,
  result=result,
  result_type=result_type,
  attempt=attempt,
+ start_timestamp_millis=start_timestamp_millis,
  ):
  self._emit_mcp(mcp, emitter, callback)