RFR: 8304711: Combine G1 root region abort and wait into a single method [v2]

[Thomas Schatzl]

> Hi all,
> 
>   merge root region scan and abort calls into a single method as they are used together twice; this also helps with [JDK-8300770](https://bugs.openjdk.org/browse/JDK-8300770) later.
> 
> Testing: gha
> 
> Thanks,
>   Thomas

Thomas Schatzl has updated the pull request incrementally with one additional commit since the last revision:

  ayang review

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Changes:
  - all: https://git.openjdk.org/jdk/pull/13145/files
  - new: https://git.openjdk.org/jdk/pull/13145/files/ead9ea7d..acdd5adc

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=13145&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=13145&range=00-01

  Stats: 2 lines in 1 file changed: 0 ins; 2 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13145.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13145/head:pull/13145

PR: https://git.openjdk.org/jdk/pull/13145