Changes

CPU and process util stats

They are measured between GC STW points, excluding GC STW points
themselves.

They are reported at GC start point in Verbose GC as percentages, but
there are also plans to use them for some future heuristics.

A sample report line, showing how and where it's reported:

```
<gc-start id="190" type="scavenge" contextid="189"
timestamp="2024-07-22T09:17:33.286">
  <cpu-util id="191" total="80.44" process="68.95" />
  <mem-info id="192" free="1438506168" total="10737418240" percent="13">
```

Signed-off-by: Aleksandar Micic <Aleksandar_Micic@ca.ibm.com>
 (commit: 21103f6)