WIP: Upgrade to lucene 9.7.0

[steffenvan]

Attempting to update Lucene to its latest version, which currently stands at 9.7.0. The code contains several TODOs since the refactoring process is a bit complex, and I have added empty and/or "wrong" implementations for some of the abstract functions. Moreover, there are design decisions that require expertise I currently lack. As it stands, the core code should compile, but the tests won't.