Need a non-shared QHash

Now that QHash competes favourably with its STL counterpart again, we're missing a non-shared version of it. So far, we were able to use the STL containers for containers that weren't shared:

• QList → std::vector / QVarLengthArray
• QMap → std::map{{}}
• Q5Hash → std::unordered_map
• Q6Hash → ???

QFlatMap is a candidate, but that has different performance characteristics, in particular, it's not well-suited for mixed inserts and removals.

What we really need, though, is a, say, QHashTable that's not implicitly shared, but otherwise like QHash.