RFR: 8342508: Use latch in BasicMenuUI/bug4983388.java instead of delay [v3]

[Alexey Ivanov]

> Use a `CountDownLatch` in `javax/swing/plaf/basic/BasicMenuUI/4983388/bug4983388.java` instead of delay.
> 
> The latch provides a direct way to synchronise EDT and main thread, the test will finish quicker.
> 
> I ran the updated test a few times with `JTREG=REPEAT_COUNT=20`, the test always passed in the CI.

Alexey Ivanov has updated the pull request incrementally with one additional commit since the last revision:

  Use method reference to dispose of the frame

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Changes:
  - all: https://git.openjdk.org/jdk/pull/21585/files
  - new: https://git.openjdk.org/jdk/pull/21585/files/53d03a32..616627e9

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=21585&range=02
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=21585&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 0 del; 1 mod
  Patch: https://git.openjdk.org/jdk/pull/21585.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/21585/head:pull/21585

PR: https://git.openjdk.org/jdk/pull/21585