RFR: 8338995: New Object to ObjectMonitor mapping: PPC64 implementation

[Martin Doerr]

PPC64 implementation of [JDK-8315884](https://bugs.openjdk.org/browse/JDK-8315884).

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Commit messages:
 - 8338995: New Object to ObjectMonitor mapping: PPC64 implementation

Changes: https://git.openjdk.org/jdk/pull/20922/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20922&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8338995
  Stats: 166 lines in 8 files changed: 76 ins; 27 del; 63 mod
  Patch: https://git.openjdk.org/jdk/pull/20922.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20922/head:pull/20922

PR: https://git.openjdk.org/jdk/pull/20922