RFR: 2317: Avoid use of deprecated Thread.getId()

[Pavel Rappo]

`Thread.getId()` was deprecated in JDK 19, as part of [JDK-8284161]. Skara build now produces warnings because of that method:

    Task :bot:compileTestJava
    Note: skara/bot/src/test/java/org/openjdk/skara/bot/BotTaskAggregationHandlerTests.java uses or overrides a deprecated API.

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

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Commit messages:
 - Initial commit

Changes: https://git.openjdk.org/skara/pull/1669/files
  Webrev: https://webrevs.openjdk.org/?repo=skara&pr=1669&range=00
  Issue: https://bugs.openjdk.org/browse/SKARA-2317
  Stats: 4 lines in 1 file changed: 0 ins; 0 del; 4 mod
  Patch: https://git.openjdk.org/skara/pull/1669.diff
  Fetch: git fetch https://git.openjdk.org/skara.git pull/1669/head:pull/1669

PR: https://git.openjdk.org/skara/pull/1669