RFR: JDK-8304820: Statically allocate ObjectSynchronizer mutexes

[Justin King]

Similar to https://git.openjdk.org/jdk/pull/13143, statically allocate mutexes which live for the lifetime of the process.

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Commit messages:
 - Statically allocate ObjectSynchronizer mutexes

Changes: https://git.openjdk.org/jdk/pull/13160/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13160&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8304820
  Stats: 9 lines in 1 file changed: 0 ins; 1 del; 8 mod
  Patch: https://git.openjdk.org/jdk/pull/13160.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13160/head:pull/13160

PR: https://git.openjdk.org/jdk/pull/13160