Setting default comparator for namespace_map to be the expected behaviour.

[GhostofCookie]

Very interesting stuff this comparator, learning new stuff all the time. The test looks like a lot has changed, but hilariously, it was working exactly as intended. The changes to the test are just general cleanup, they do NOT change it's behaviour at all.

The big change here is that the default comparator for quicr::namespace_map is now std::greater instead of std::less. The reason for this is simple: My original assumption about what was being found was wrong. The real behaviour:

• When sorting with std::less, when using a quicr::Name to index it, the shortest match will be returned.
• When sorting with std::greater, when using a quicr::Name to index it, the longest match will be returned.

For whatever reason, I seemed to have this reversed in my head, and yet still wrote the correct test that showed that exact result. I suppose the way the test was written before was vague and unhelpful. So, the cleanup of the test and some added comments to the type itself should clear up the issue.

Also changed, but not really important: quicr::namespace_map is now a concrete type inheriting from std::map, instead of just being an alias.