Drop support for Java 8 (and 11?)

[gaeljw]

While it's not a blocker for us in terms of maintenance today, the community has moved on and all major frameworks/libs already dropped support for Java 8 or even Java 11.

We should do it as well in the next major.

It probably make sense to wait for Cucumber JVM to do so as well before we do it. They'll do it in next major: cucumber/cucumber-jvm#2962.