RFR: 8281966: Absolute path of symlink is null in JFileChooser [v4]

[Tejesh R]

> Absolute path of Symbolic Link created in Windows is set to `null` in `BasicFileChooserUI` class. This happens when propertyChangeListener is implemented to get the Symbolic link's Absolute path on Mouse click through JFileChooser. The reason being that on click of Symbolic link, the _ValueChanged()_ in `BasicFileChooserUI` class has a logic which actually sets the  `chooser.SelectedFile()` to `null` even though the path is not null. Hence the issue is addressed by checking if its a Symbolic link and then setting the `chooser.SelectedFile()` to the value of clicked link without modifying the other logics.

Tejesh R has updated the pull request incrementally with one additional commit since the last revision:

  Fix for multi selection and updated the test to handle both single and multi selection

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Changes:
  - all: https://git.openjdk.org/jdk/pull/9597/files
  - new: https://git.openjdk.org/jdk/pull/9597/files/985a7e75..dc315aa1

Webrevs:
 - full: https://webrevs.openjdk.org/?repo=jdk&pr=9597&range=03
 - incr: https://webrevs.openjdk.org/?repo=jdk&pr=9597&range=02-03

  Stats: 87 lines in 2 files changed: 50 ins; 11 del; 26 mod
  Patch: https://git.openjdk.org/jdk/pull/9597.diff
  Fetch: git fetch https://git.openjdk.org/jdk pull/9597/head:pull/9597

PR: https://git.openjdk.org/jdk/pull/9597