RFR: 8330577: If the JFR event jdk.G1HeapRegionTypeChange is enabled, it is also written without region type change

[Andreas Steiner]

Avoid to report jdk.G1HeapRegionTypeChange event if G1 region type is set to free even it is of type free already.

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Commit messages:
 - JDK-8330577

Changes: https://git.openjdk.org/jdk/pull/18949/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18949&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8330577
  Stats: 3 lines in 1 file changed: 2 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/18949.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18949/head:pull/18949

PR: https://git.openjdk.org/jdk/pull/18949