RFR: 8341162: Open source some of the AWT window test

[Jayathirth D V]

Clean up and open source some of the AWT window tests.
Automated test `OwnedWindowShowTest.java` is verified in our CI also and it passes on all platforms.

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Commit messages:
 - 8341162: Open source some of the AWT window test

Changes: https://git.openjdk.org/jdk/pull/21284/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=21284&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8341162
  Stats: 341 lines in 4 files changed: 341 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/21284.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21284/head:pull/21284

PR: https://git.openjdk.org/jdk/pull/21284