A prefix was a Vec of its bytes: a heap allocation for every prefix parsed,
stored or copied, and a variable-length key to hash. It is now twenty
bytes, Copy, with private fields and one representation; `bytes()` gives
the wire form.
On the full-table benchmark this alone takes decoding from 9.3 to 10.7
million routes a second and inserting into the Adj-RIB-In from 2.9 to 3.6.
Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>
