ata-validator

Constructing a validator no longer clones and serializes every schema to find out whether it needed normalizing. It did that on the root and on each registered schema: serialize, deep clone, normalize the clone, serialize again, compare. For a schema with no nullable field and no draft-07 keyword the answer is always no, and the work was thrown away. Every question the normalizers ask is whether some key appears anywhere in the tree, so one walk answers all of them, and the clone now happens only for schemas that need it. No registry and ten fields goes from 18.5 to 4.6 µs; fifty registered schemas of fifty fields, which is a small server's worth, from 2570 to 260 µs.