RFR: 8306575: Clean up and open source four Dialog related tests

[Alexander Zuev]

Cleaned up and stabilized four Dialog-related tests.

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Commit messages:
 - 8306575: Clean up and open source four Dialog related tests

Changes: https://git.openjdk.org/jdk/pull/13592/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=13592&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306575
  Stats: 585 lines in 4 files changed: 585 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/13592.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/13592/head:pull/13592

PR: https://git.openjdk.org/jdk/pull/13592