Create a JUnit5-compatible utility to capture screenshots of failed headful tests. The idea is that a certain annotation can be added to an intermittently failing test or a test that fails on a certain platform to capture the screenshot for debugging:

```
@ExtendWith(ScreenCaptureTestWatcher.class)
```

Screenshots of the primary screen will be captured in PNG format, encoded to a Base64 string, and logged to stderr.
A special utility is then needed to extract the actual screenshot image from the log file (I am thinking of Monkey Tester, but it can be a standalone app or a script).

QUESTIONS

- stdout or stderr?
- format? hex/base64?
- should it emit a valid JSON segment to be compatible with any log viewer applications that understand JSON? i.e. `{ screenshot:"...base64..." }`
- do we need a separate decoder script or Monkey Tester is enough?

MAILING LIST

https://mail.openjdk.org/pipermail/openjfx-dev/2024-March/046124.html
https://mail.openjdk.org/pipermail/openjfx-dev/2024-March/046125.html