Add ability to read configuration from jpackage `lib/app/<app>.cfg` file

[ctrueden]

In case an app was packaged by jpackage, there will be a file in lib/app ending in .cfg of the form:

[Application]
app.classpath=$APPDIR/qupath-app-0.5.0.jar
app.mainclass=qupath.QuPath
app.classpath=$APPDIR/aircompressor-0.21.jar
...
app.classpath=$APPDIR/xmpcore-6.1.11.jar

[JavaOptions]
java-options=-Djpackage.app-version=0.5.0
java-options=-Xmx14336M

Jaunch could be enhanced to read such files and augment its JaunchConfig accordingly, to avoid needing to reiterate the same configuration in two different configuration files.

[imagesc-bot]

This issue has been mentioned on Image.sc Forum. There might be relevant details there:

https://forum.image.sc/t/jaunch-a-new-java-launcher-test-fiji-with-java-21/92058/1