[jdk17u-dev] RFR: 8316149: Open source several Swing JTree JViewport KeyboardManager tests

[Goetz Lindenmaier]

This will be a clean backport from 21 once I pushed that change and adapted the title to point to the hash in 21.

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Commit messages:
 - Backport 8316149+8316627 from 21

Changes: https://git.openjdk.org/jdk17u-dev/pull/3136/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=3136&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316149
  Stats: 370 lines in 5 files changed: 370 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/3136.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/3136/head:pull/3136

PR: https://git.openjdk.org/jdk17u-dev/pull/3136