RFR: 8353655: Clean up and open source KeyEvent related tests (Part 1)

[Alexander Zuev]

Clean up and open source three tests related to the KeyEvent mechanics.

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Commit messages:
 - 8353655: Clean up and open source KeyEvent related tests (Part 1)

Changes: https://git.openjdk.org/jdk/pull/24609/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=24609&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8353655
  Stats: 317 lines in 3 files changed: 317 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/24609.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/24609/head:pull/24609

PR: https://git.openjdk.org/jdk/pull/24609