RFR: 2318: Prefer Thread.sleep(Duration)

[Pavel Rappo]

`Thread.sleep(java.time.Duration)` was introduced in JDK 19, as part of [JDK-8284161], and standardised in JDK 21, as part of [JDK-8304919].

[JDK-8284161]: https://bugs.openjdk.org/browse/JDK-8284161
[JDK-8304919]: https://bugs.openjdk.org/browse/JDK-8304919

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/skara/pull/1670/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1670&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2318
  Stats: 22 lines in 11 files changed: 0 ins; 2 del; 20 mod
  Patch: https://git.openjdk.org/skara/pull/1670.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1670/head:pull/1670

PR: https://git.openjdk.org/skara/pull/1670