Code cleanup

[Geal]

the library has been written in a way that is not very idiomatic, mainly through using types from the vavr project. This has helped us gain confidence in the implementation by following closely the rust implementation, but it is now slowing us down. Those types should be replaced gradually, where it makes sense (not a thoughtless search and replace):

• Either -> using exceptions. This in particular should clean up a lot of the code
• option: nullable type?
• tuples -> record objects

[murdos]

• option -> Optional?

BTW using record objects (which is a good idea IMO) would require using java 17