RFR: 8280913: Create a regression test for JRootPane.setDefaultButton() method [v3]

[Manukumar V S]

> This tests the behaviour of the method JRootPane.setDefaultButton() in different platforms with different LAFs.
> As per the spec https://docs.oracle.com/en/java/javase/17/docs/api/java.desktop/javax/swing/JRootPane.html#setDefaultButton(javax.swing.JButton), "The default button is the button which will be activated when a UI-defined activation event (typically the Enter key) occurs in the root pane regardless of whether or not the button has keyboard focus (unless there is another component within the root pane which consumes the activation event, such as a JTextPane). ".
> 
> This also fixes and colocates the tonga test Swing_JButton/Automated/bug4659800 written for verifying JDK-4659800.
> 
> This test is run multiple times in different platforms and got 100% success in mac and windows, linux.

Manukumar V S has updated the pull request incrementally with one additional commit since the last revision:

  8280913: Create a regression test for JRootPane.setDefaultButton() method

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Changes:
  - all: https://git.openjdk.java.net/jdk/pull/7278/files
  - new: https://git.openjdk.java.net/jdk/pull/7278/files/72876598..9ed2cc9b

Webrevs:
 - full: https://webrevs.openjdk.java.net/?repo=jdk&pr=7278&range=02
 - incr: https://webrevs.openjdk.java.net/?repo=jdk&pr=7278&range=01-02

  Stats: 1 line in 1 file changed: 0 ins; 1 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/7278.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/7278/head:pull/7278

PR: https://git.openjdk.java.net/jdk/pull/7278