RFR: 8305370: Inconsistent use of for_young_only_phase parameter in G1 predictions

[Thomas Schatzl]

Hi all,

  please review this change to fix some inconsistent use of `for_young_only_phase`: some methods that require it are not passed that parameter, and some methods, although getting passed that parameter partially re-load that value from collector state.

Fwiw, I am aware that `G1Policy::predict_region_total_time_ms` only ever gets passed `false` as this parameter. I would have changed that as well if some [upcoming change](https://github.com/openjdk/jdk/commit/6c2f18eba29ad9f6e4e5ed28f1521037fdc49398) did not use other values as well. We can always remove it later if not necessary, but if somebody insists on doing so I will do that as well (probably separately).

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - Initial version

Changes: https://git.openjdk.org/jdk/pull/13267/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13267&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8305370
  Stats: 9 lines in 2 files changed: 2 ins; 0 del; 7 mod
  Patch: https://git.openjdk.org/jdk/pull/13267.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13267/head:pull/13267

PR: https://git.openjdk.org/jdk/pull/13267