RFR: 8331031: unify os::dont_yield and os::naked_yield across Posix platforms

[Matthias Baesken]

The os::dont_yield and os::naked_yield can be unified across Posix platforms.

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Commit messages:
 - JDK-8331031

Changes: https://git.openjdk.org/jdk/pull/18933/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=18933&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8331031
  Stats: 45 lines in 4 files changed: 8 ins; 37 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/18933.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/18933/head:pull/18933

PR: https://git.openjdk.org/jdk/pull/18933