RFR: 8315986: javax/swing/JMenuItem/4654927/bug4654927.java: component must be showing on the screen to determine its location

[Prasanta Sadhukhan]

Test was run without waiting for UI to be made visible leading to IllegalComponentStateException.
Used robot.delay consistent with other headful tests to made the test wait after UI is created and shown.

Test passed in several iterations in all platforms. Link in JBS

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Commit messages:
 - 8315986: javax/swing/JMenuItem/4654927/bug4654927.java: component must be showing on the screen to determine its location
 - 8315986: javax/swing/JMenuItem/4654927/bug4654927.java: component must be showing on the screen to determine its location

Changes: https://git.openjdk.org/jdk/pull/15677/files
 Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=15677&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8315986
  Stats: 34 lines in 1 file changed: 13 ins; 6 del; 15 mod
  Patch: https://git.openjdk.org/jdk/pull/15677.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/15677/head:pull/15677

PR: https://git.openjdk.org/jdk/pull/15677