Checkmk Werk 15902: CPU utilization: Make core numbering consistent

ID: 15902 Title: CPU utilization: Make core numbering consistent Component: metrics Level: 1 Class: Bug fix Version: 2.3.0b1 Currently, the cores shown for the per core utilization are numbered starting at 1, while elsewhere the numbering starts at 0. This has been made consistent by changing the start to 0 for the per core utilization as well.