RFR: 8273617: UninitializedDisplayModeChangeTest.java times out on macOS 12 [v2]

[Prasanta Sadhukhan]

> Test used to timeout even though it seems the test passed..Increased the timeout to a safe value as sometimes it shows elapsed time to timeout > 300secs in macOS in CI and also ensured the wait-time for child process to execute the test is not been waiting endlessly.
> Also ensured the original display mode is resetted after the test to prevent affecting following tests.
> 
> Tried 100 iterations of the fix on all platforms which is ok

Prasanta Sadhukhan has updated the pull request incrementally with one additional commit since the last revision:

  EDT fix, timeout reduced

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Changes:
  - all: https://git.openjdk.org/jdk/pull/27365/files
  - new: https://git.openjdk.org/jdk/pull/27365/files/5438669e..cff787a5

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=27365&range=01
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=27365&range=00-01

  Stats: 42 lines in 2 files changed: 14 ins; 16 del; 12 mod
  Patch: https://git.openjdk.org/jdk/pull/27365.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/27365/head:pull/27365

PR: https://git.openjdk.org/jdk/pull/27365