[jdk21u] RFR: 8316017: Refactor timeout handler in PassFailJFrame

[Alexey Ivanov]

This changeset cleans up timeout handling PassFailJFrame which is a manual test framework. It affects only the internals of the class. 

Clean backport. Low risk.

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Commit messages:
 - Backport 3abd772672a4dfd984459283235f3b1d8fb28a49

Changes: https://git.openjdk.org/jdk21u/pull/387/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk21u&pr=387&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8316017
  Stats: 149 lines in 1 file changed: 92 ins; 33 del; 24 mod
  Patch: https://git.openjdk.org/jdk21u/pull/387.diff
  Fetch: git fetch https://git.openjdk.org/jdk21u.git pull/387/head:pull/387

PR: https://git.openjdk.org/jdk21u/pull/387