RFR: 8338658: New Object to ObjectMonitor mapping: s390x implementation [v4]

[Amit Kumar]

> s390x implementation of [JDK-8315884](https://bugs.openjdk.org/browse/JDK-8315884) New Object to ObjectMonitor mapping; 
> 
> Testing: 
> - tier1-test (fastdebug)
> - tier1-test with UseObjectMonitorTable (fastdebug)
> - tier1-test with UseObjectMonitorTable (release)

Amit Kumar has updated the pull request with a new target base due to a merge or a rebase. The pull request now contains four commits:

 - Merge branch 'master' into om_v0
 - only use z_mvghi instruction
 - review comments
 - s390-port

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Changes: https://git.openjdk.org/jdk/pull/20740/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=20740&range=03
  Stats: 167 lines in 7 files changed: 92 ins; 23 del; 52 mod
  Patch: https://git.openjdk.org/jdk/pull/20740.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/20740/head:pull/20740

PR: https://git.openjdk.org/jdk/pull/20740