RFR: 8327383: Clean up _Stalled and _Spinner fields

[Fredrik Bredberg]

Removed the `_Stalled` and the `_Spinner` fields from the object synchronization code, since they are not used anymore.

Passes tier1-5

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Commit messages:
 - 8327383: Clean up _Stalled and _Spinner fields

Changes: https://git.openjdk.org/jdk/pull/18306/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18306&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8327383
  Stats: 17 lines in 4 files changed: 0 ins; 17 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18306.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18306/head:pull/18306

PR: https://git.openjdk.org/jdk/pull/18306