Test Jandex 3.0

[Azquelt]

Jandex is getting close to a 3.0 release with breaking changes, we should see how much work is needed to update and whether there are any issues.

There are changes to the serialization format so we will at least need to update the sparse index reader.

Some new APIs were backported in 2.4.3 to make migration easier, so we may want to update to that first.

[Azquelt]

Kernel team now have their own issue for this.