Add Java 13 CI

[snicoll]

We need to update CI to build against Java 13 as well.

I also noticed quite by accident that -Xverify:none and -noverify are going to be deprecated in this release. We have several places where this is used so we should decide what to do there.

[snicoll]

Rampdown phase two is scheduled for mid-July so let's resume work on this one around that time.

[snicoll]

There are some Hazelcast tests failing on Java 13, I've opened hazelcast/hazelcast#15348