Remove Matcher class

[johnarevalo]

With the duckdb implementation in 0.5 the Matcher and MatcherMultilabel classes should be removed.

[axiomcura]

Hey @johnarevalo! Since I use the Matcher class to validate whether my pairs are being correctly assigned, is there another way to confirm that the pairs set via Metadata are correctly configured? If not, I believe this could be a great opportunity to introduce a function or a tutorial that demonstrates how to verify whether the expected pairs are correctly set.