RFR: 8364423: G1: Refactor G1UpdateRegionLivenessAndSelectForRebuildTask

[Thomas Schatzl]

Hi all,

  please review this refactoring of `G1UpdateRegionLivenessAndSelectForRebuildTask` to remove some code duplication, which makes it simpler to add more common code

Testing: gha

Thanks,
  Thomas

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Commit messages:
 - * fix whitespace
 - 8364423

Changes: https://git.openjdk.org/jdk/pull/26574/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=26574&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8364423
  Stats: 46 lines in 1 file changed: 19 ins; 21 del; 6 mod
  Patch: https://git.openjdk.org/jdk/pull/26574.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/26574/head:pull/26574

PR: https://git.openjdk.org/jdk/pull/26574