RFR: 8348299: Update List/ItemEventTest/ItemEventTest.java

[Alexey Ivanov]

With this changeset, I update the `java/awt/List/ItemEventTest/ItemEventTest.java` test to improve its stability and analysis of failures of the test.

1. Use thread-safe `StringBuffer` for `actualSelectionOrder` to track selecting/deselecting items in the list.
2. Enable `robot.setAutoWaitForIdle(true)` and remove `robot.waitForIdle()` from the test code.
3. Log `handleEvent` and `ItemListener` which helps to identify test failures.  
    (In case of [JDK-8204221](https://bugs.openjdk.org/browse/JDK-8204221), `handleEvent` is never logged.)
5. Take screenshot of the list on failure;  
    Optionally take screenshot after each mouse press+release if `-save` is passed as a parameter to the test.

The updated test passes.

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Commit messages:
 - 8348299: Update List/ItemEventTest/ItemEventTest.java

Changes: https://git.openjdk.org/jdk/pull/23238/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=23238&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8348299
  Stats: 100 lines in 1 file changed: 46 ins; 8 del; 46 mod
  Patch: https://git.openjdk.org/jdk/pull/23238.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/23238/head:pull/23238

PR: https://git.openjdk.org/jdk/pull/23238