chore(engine): configure test fork count via property
chore(engine): configure test fork count via property

- this enables us to override the value via command line

related to CAM-10568

camunda/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,langfr/camunda-bpm-platform,falko/camunda-bpm-platform,camunda/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,falko/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,falko/camunda-bpm-platform,camunda/camunda-bpm-platform,langfr/camunda-bpm-platform,camunda/camunda-bpm-platform,langfr/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,falko/camunda-bpm-platform,falko/camunda-bpm-platform,camunda/camunda-bpm-platform,camunda/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,ingorichtsmeier/camunda-bpm-platform,falko/camunda-bpm-platform,langfr/camunda-bpm-platform,langfr/camunda-bpm-platform,langfr/camunda-bpm-platform