RFR: 8008222: [macosx] selectNextChangeLead is not implemented for Tree in Aqua LAF

[Prasanta Sadhukhan]

There is no shortcuts for selectNextChangeLead and selectPreviousChangeLead in Aqua LAF which updates [LEAD_SELECTION_PATH_PROPERTY](https://docs.oracle.com/en/java/javase/24/docs/api/java.desktop/javax/swing/JTree.html#LEAD_SELECTION_PATH_PROPERTY).....
Other L&F uses "ctrl DOWN/UP" to selectNextChangeLead/selectPreviousChangeLead but same shortcut cannot be used in mac as "ctrl DOWN" shortcut is used to display the window of current active application while "ctrl UP" is used to display all windows of all applications which allows to switch between them
so used CTRL+SHIFT+DOWN for the selectNextChangeLead CTRL+SHIFT+UP for selectPreviousChangeLead

No regression test as it can be verified through SwingSet2 demo as below..

With ctrl+shift+down
<img width="124" alt="Screenshot 2025-06-19 at 1 41 39 PM" src="https://github.com/user-attachments/assets/8baa386e-b03a-4fd2-b5e2-4ac26157e5af" />

another ctrl+shift+down
<img width="127" alt="Screenshot 2025-06-19 at 1 42 39 PM" src="https://github.com/user-attachments/assets/572a806c-4d54-4045-b92a-c1e88d403305" />

Now, ctrl+shift+up
<img width="134" alt="Screenshot 2025-06-19 at 1 44 51 PM" src="https://github.com/user-attachments/assets/6d671852-f7b7-434f-8688-6c5dd4b3cdb5" />

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Commit messages:
 - Add shortcut

Changes: https://git.openjdk.org/jdk/pull/25892/files
  Webrev: https://webrevs.openjdk.org/?repo=jdk&pr=25892&range=00
  Issue: https://bugs.openjdk.org/browse/JDK-8008222
  Stats: 4 lines in 1 file changed: 4 ins; 0 del; 0 mod
  Patch: https://git.openjdk.org/jdk/pull/25892.diff
  Fetch: git fetch https://git.openjdk.org/jdk.git pull/25892/head:pull/25892

PR: https://git.openjdk.org/jdk/pull/25892