Missing gc time in zgc generational logging

[Mike Millson]

There seems to be a lot of missing gc time in the jdk21 zgc generational
logging.

Following is an example (complete log attached).

The gc time below is .234ms, and the safepoint is 2.7ms
(1900085+806967+4204/10^6).

It's over an order of magnitude off.

[2023-12-12T10:20:45.260+0200][info][gc,phases   ] GC(34) y: Pause Mark
Start 0.234ms
[2023-12-12T10:20:45.260+0200][info][safepoint   ] Safepoint
"ZMarkStartYoung", Time since last: 9642266719 ns, Reaching safepoint:
1900085 ns, Cleanup: 4204 ns, At safepoint: 806967 ns, Total: 2711256 ns

Thank you,
Mike
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