RFR: 8330577: G1 sometimes sends jdk.G1HeapRegionTypeChange for non-changes

[Thomas Schatzl]

Hi all,

  please review this change that avoids posting Free->Free and Old->Old region transitions in JFR.

The reason for these could have been:
  * Free->Free: heap shrinking and full gc
  * Old->Old: heap shrinking, full gc or evacuation failure in an old region

Parts of this change has been contributed by @ansteiner , crediting him for this (the first commit).

Testing: tier1-3, tier5, all "detailed" JFR test cases

Thanks,
  Thomas

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Commit messages:
 - Fix errorneous Old->Old transitions which actually were Free->Old.
 - JDK-8330577

Changes: https://git.openjdk.org/jdk/pull/19389/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=19389&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330577
  Stats: 112 lines in 2 files changed: 110 ins; 0 del; 2 mod
  Patch: https://git.openjdk.org/jdk/pull/19389.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/19389/head:pull/19389

PR: https://git.openjdk.org/jdk/pull/19389