RFR: 8344302: G1: Refactor G1CMTask::do_marking_step to use smaller wrapper methods

[Ivan Walulya]

Hi all,

Please review this refactoring of G1CMTask::do_marking_step, breaking it down into multiple helper methods to improve readability.

Testing: Tier-1

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Commit messages:
 - rename handle_abort
 - removed debug
 - Merge branch 'master' into MarkingRestart
 - simple refactor
 - pitstop

Changes: https://git.openjdk.org/jdk/pull/22147/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=22147&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8344302
  Stats: 432 lines in 2 files changed: 223 ins; 195 del; 14 mod
  Patch: https://git.openjdk.org/jdk/pull/22147.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/22147/head:pull/22147

PR: https://git.openjdk.org/jdk/pull/22147