[jdk25u-dev] RFR: 8342401: [TESTBUG] javax/swing/JSpinner/8223788/JSpinnerButtonFocusTest.java test fails in ubuntu 22.04 on SBR Hosts

[Roland Mesde]

Backporting JDK-8342401: [TESTBUG] javax/swing/JSpinner/8223788/JSpinnerButtonFocusTest.java test fails in ubuntu 22.04 on SBR Hosts.

This PR fixes intermittent JSpinnerButtonFocusTest.java failures caused by timing issues between UI creation and test execution. It adds proper delays, centers frame positioning, and moves listener registration.

For parity with Oracle JDK.

Ran related tests on linux-x64, linux-aarch64, macos-aarch64 and windows-x64:

make test TEST=test/jdk/javax/swing/JSpinner/8223788/JSpinnerButtonFocusTest.java

Results attached:

[windows-x64-specific-test.log](https://github.com/user-attachments/files/25298720/windows-x64-specific-test.log)
[macos-aarch64-specific-test.log](https://github.com/user-attachments/files/25298721/macos-aarch64-specific-test.log)
[linux-x64-specific-test.log](https://github.com/user-attachments/files/25298722/linux-x64-specific-test.log)
[linux-aarch64-specific-test.log](https://github.com/user-attachments/files/25298723/linux-aarch64-specific-test.log)

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Commit messages:
 - Backport 55787fe5f52544ea902cac35f1f552e26d954167

Changes: https://git.openjdk.org/jdk25u-dev/pull/262/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk25u-dev&pr=262&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8342401
  Stats: 24 lines in 1 file changed: 10 ins; 9 del; 5 mod
  Patch: https://git.openjdk.org/jdk25u-dev/pull/262.diff
  Fetch: git fetch https://git.openjdk.org/jdk25u-dev.git pull/262/head:pull/262

PR: https://git.openjdk.org/jdk25u-dev/pull/262