[jdk17u-dev] RFR: 8306850: Open source AWT Modal related tests

[Victor Rudometov]

Clean backport, new tests, low risk
Checked on macOS x64, linux x64, windows x64: tests pass

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Commit messages:
 - Backport 41ba05e450ed4467535bcee81946099e38665c3f

Changes: https://git.openjdk.org/jdk17u-dev/pull/1369/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk17u-dev&pr=1369&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8306850
  Stats: 1053 lines in 6 files changed: 1053 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk17u-dev/pull/1369.diff
  Fetch: git fetch https://git.openjdk.org/jdk17u-dev.git pull/1369/head:pull/1369

PR: https://git.openjdk.org/jdk17u-dev/pull/1369