RFR: 8293623: Simplify G1ConcurrentRefineThreadControl [v6]

[Lei Zaakjyu]

> 8293623: Simplify G1ConcurrentRefineThreadControl

Lei Zaakjyu has updated the pull request incrementally with one additional commit since the last revision:

  refactor

-------------

Changes:
  - all: https://git.openjdk.org/jdk/pull/17077/files
  - new: https://git.openjdk.org/jdk/pull/17077/files/e028272e..4e44ba2d

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17077&range=05
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17077&range=04-05

  Stats: 42 lines in 2 files changed: 9 ins; 12 del; 21 mod
  Patch: https://git.openjdk.org/jdk/pull/17077.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17077/head:pull/17077

PR: https://git.openjdk.org/jdk/pull/17077