RFR: 8341162: Open source some of the AWT window test [v2]

[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.

Jayathirth D V has updated the pull request incrementally with two additional commits since the last revision:

 - Remove not needed setVisible calls
 - Update based on review comments

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21284/files
  - new: https://git.openjdk.org/jdk/pull/21284/files/b6492660..f53ca0d1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21284&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21284&range=00-01

  Stats: 19 lines in 4 files changed: 4 ins; 8 del; 7 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