RFR: 8325082: Rename headers named 'heapRegion*' of G1 [v5]

[Lei Zaakjyu]

> 8325082: Rename headers named 'heapRegion*' of G1

Lei Zaakjyu has updated the pull request with a new target base due to a merge or a rebase. The incremental webrev excludes the unrelated changes brought in by the merge/rebase. The pull request contains five additional commits since the last revision:

 - Merge branch 'master' of https://git.openjdk.org/jdk into JDK-8325082
 - rename
 - fix
 - reorder some headers
 - rename

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Changes:
  - all: https://git.openjdk.org/jdk/pull/17666/files
  - new: https://git.openjdk.org/jdk/pull/17666/files/faa6f661..11628202

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=17666&range=04
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=17666&range=03-04

  Stats: 32057 lines in 1054 files changed: 14510 ins; 11387 del; 6160 mod
  Patch: https://git.openjdk.org/jdk/pull/17666.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/17666/head:pull/17666

PR: https://git.openjdk.org/jdk/pull/17666