Finished & RunningProcessInstanceFetcher use the max page config value for activityInstances instead of processInstances.

AT:

• Finished & RunningProcessInstanceFetcher use getEngineImportProcessInstanceMaxPageSize

Note:
While fixing this a more severe bug in the import was uncovered and fixed:
For the edge-case that there were no nextPage results but results for the exact previous timestamp, the import was not done for the entities returned by the exact timestamp query.