RFR: 8349836: G1: Improve group prediction log message

[Thomas Schatzl]

Hi all,

  please review this minor change to the group prediction log message
printed with gc+ergo+cset=trace:

  * add group id to be able to refer to something concrete when discussing results
  * add total time
  * fix typo in `bytes_to_cop`

Testing: gha, local verification

Thanks,
  Thomas

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Commit messages:
 - 8349836

Changes: https://git.openjdk.org/jdk/pull/23562/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23562&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8349836
  Stats: 12 lines in 1 file changed: 7 ins; 3 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/23562.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23562/head:pull/23562

PR: https://git.openjdk.org/jdk/pull/23562