Only keeping strobemer matches with minimum strobes distance difference

[NicolasBuchin]

A small change that changes the heuristic on adding strobemer matches, now we just keep the ones with the closest distance to the strobemer hit on the query. Not a very noticeable difference on results but should make chaining a tiny bit faster.

[marcelm]

Hi, I’ve run our benchmark on this commit and the previous one and don’t see any difference, not in accuracy but also not in runtime:

• ends-se-time.pdf
• ends-se-accuracy.pdf

I therefore suggest to not merge this PR as it just adds (a little bit of) complexity.