Make it possible to develop plugin with IntelliJ 2023.3

[de-jcup]

Situation

Currently there were problems when importing the plugin repository into IntelliJ 2023.3 community edition for development.

Wanted

Shall work out of the box

Solution

• fix gradle setup, use newer gradle version (which supports Java 17)
• use newer jebtrains plugin (gradle)
• setup source and target compatibilities