Set Java 17 as minimum required Java version
Java 17 (LTS) is now well adopted and continuing to support Java 8 (now over 8 years old) makes little sense as a starting point for a new plugin. Bump the minimum required version to Java 17.
We considered making the minimum Java 11. But it seems that after Java 8, most users opted to skip the Java 11 LTS and jump to Java 17 instead. (See https://spring.io/blog/2022/03/28/an-update-on-java-17-adoption for some research on the topic).