Make `#@script` directive with `language` key, to disambig Jython vs Python

[ctrueden]

The scripting-python repository enables true Python scripting via the scyjava project. But it clashes with scripting-jython. Let's let scripts declare their intended language.

[imagesc-bot]

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

https://forum.image.sc/t/fiji-2024-year-in-review-milestones-and-roadmap/109418/15