RFR: 8283245: Create a test for JDK-4670319

[Srinivas Mandalika]

Write an automated regression test for  JDK-4670319

Issue
When a JTree node is expanded or collapsed, an Accessibility PropertyChange event is fired with the old state of "collapsed" and new state of "expanded" (or vice versa). The problem is that the source of the event is the AccessibeJTree, and not the AccessibleJTreeNode. This means that an assistive technology listening to this event is unable to report to the user what node was expanded/collapsed.

Fix
Fix for [JDK-4670319](https://bugs.openjdk.java.net/browse/JDK-4670319) addresses the above issue.  When tree node is expanded/collapsed, PropertyChangeEventSource is the Node.
This review is for a test for validating the above issue.

This review is for migrating tests from a closed test suite to open.

Testing:
The test ran successfully on Mach5 with multiple runs (30) on windows-x64, linux-x64 and macos-x64.

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Commit messages:
 - 8283245: Create a test for JDK-4670319

Changes: https://git.openjdk.java.net/jdk/pull/8012/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8012&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8283245
  Stats: 111 lines in 1 file changed: 111 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8012.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8012/head:pull/8012

PR: https://git.openjdk.java.net/jdk/pull/8012