RFR: JDK-8287261: [macos] JList Focus Ring color doesn't follow Accent color changes on macOS

[Harshitha Onkar]

With the proposed fix, JList's focus ring color follows accent color changes. Previously the focus ring for JList was not prominently visible and did not follow accent color changes.

While investing a similar issue related to JTable (https://github.com/openjdk/jdk/pull/7768#discussion_r839813517), it was observed that List.focusCellHighlightBorder was using the cellFocusRing color as well. This PR extends the focus ring accent color changes to JLists. 

Related issues: [JDK-7124282](https://bugs.openjdk.java.net/browse/JDK-7124282) , [JDK-8261243](https://bugs.openjdk.java.net/browse/JDK-8261243)

####    Summary of changes

-  focusCellHighlightBorder in `AquaLookAndFeel` changed which is used for cell border for lists and tables
-  code related to on-the-fly focus ring color refactored into a separate method (`changeFocusRingColor()`) for re-usability 
-  `changeFocusRingColor()` called when PropertyChangeEvent == FRAME_ACTIVE_PROPERTY and the frame gains focus, instead of calling in individual `swapSelectionColors` in `AquaFocusHandler.java`
- Common test added - `CellFocusRingTest`, which tests for both cases - Tables & Lists. 

**Before and After screenshots of JList** _(Screenshots from SwingSet2 demo)_

![Screen Shot 2022-05-25 at 3 55 49 PM](https://user-images.githubusercontent.com/95945681/170382727-54ed155b-6f08-4c75-8657-89c15764e1cd.png)

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Commit messages:
 - focus ring changes for JList

Changes: https://git.openjdk.java.net/jdk/pull/8896/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8896&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8287261
  Stats: 377 lines in 4 files changed: 189 ins; 162 del; 26 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8896.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8896/head:pull/8896

PR: https://git.openjdk.java.net/jdk/pull/8896