RFR: 8284521: Write an automated regression test for RFE 4371575

[Manukumar V S]

Write an automated regression test for [JDK-4371575](https://bugs.openjdk.java.net/browse/JDK-4371575)

Issue:
As part of the Merlin focus project, JComponent.setRequestFocusEnabled was
deprecated and its implementation was changed to map exactly to the new
method Component.setFocusable. Scott believes that the old behavior may be
preferable. He would like to be able to specify that a Component is focusable,
and should receive focus during keyboard traversal, but that it should not
automatically take focus when the user clicks on it with the mouse.

We are concerned that the accessibility team would be against this behavior,
and this also seems like more of a PLAF issue. Nevertheless, we should look
into it before beta ships.

Fix:
After some discussion we decided that the best balance of the old and new would be to make this an advisory property. This property will not be synonymous with focusable. Instead our mouse listeners will check this property before requesting focus. This provides as closely as possible the old behavior, while allowing people to use the new focusable property if they don't want a component focusable at all.

Testing:
Tested in mach5, 10 times with all the 3 available platform like macosx, windows and linux and got all Pass.

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Commit messages:
 - 8284521: Write an automated regression test for RFE 4371575

Changes: https://git.openjdk.java.net/jdk/pull/8143/files
 Webrev: https://webrevs.openjdk.java.net/?repo=jdk&pr=8143&range=00
  Issue: https://bugs.openjdk.java.net/browse/JDK-8284521
  Stats: 138 lines in 1 file changed: 138 ins; 0 del; 0 mod
  Patch: https://git.openjdk.java.net/jdk/pull/8143.diff
  Fetch: git fetch https://git.openjdk.java.net/jdk pull/8143/head:pull/8143

PR: https://git.openjdk.java.net/jdk/pull/8143