[14] Review Request: 8233827 Enable screenshots in the enhanced failure handler on Linux/macOS

[Sergey Bylokhov]

Hello.
Please review the fix for JDK 14.

Bug: https://bugs.openjdk.java.net/browse/JDK-8233827
Fix: http://cr.openjdk.java.net/~serb/8233827/webrev.01

This change adds the "screen capture on the test failure" feature on macOS and Linux.
  - On Linux, it is implemented by the "gnome-screenshot" command(in case of
    multiscreen+xinerama    the whole big screen will be saved to the "screen.png" file).
  - On macOS it is implemented by the "screencapture" command, note that I have
    used 1 file per screen, if the number of screens less than 5, other files will be ignored.

-- 
Best regards, Sergey.