RFR: JDK-8348302 : [Test bug] Update FileDialogIconTest.java

[Harshitha Onkar]

FileDialogIconTest.java has been updated.

Following changes were made.

-  Test instructions updated
-  BugID associated with the test is updated to the correct one
-  setIconBufferedImagesToFrame and setIconBufferedImagesToDialog btns added to the frame.
-  other minor cleanups

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Commit messages:
 - test changes

Changes: https://git.openjdk.org/jdk/pull/23523/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23523&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348302
  Stats: 95 lines in 1 file changed: 31 ins; 5 del; 59 mod
  Patch: https://git.openjdk.org/jdk/pull/23523.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23523/head:pull/23523

PR: https://git.openjdk.org/jdk/pull/23523