New vitaminc-ore crate: one order encoding per kind, with block ORE, CLLW ORE and CLLW OPE as pluggable schemes #374

Background

An order term lets the database answer <, > and ORDER BY on
encrypted values. EQL stores two order schemes: block ORE (in ore-rs) and
CLLW OPE (in cllw-ore). Both take bytes whose order is the value's order, then
encrypt them.

Problem

1. Each scheme encodes plaintext its own way. cllw-ore hand-rolls integers and
   floats, and keeps -0.0 distinct from +0.0 where orderable-bytes
   folds it.
2. Stack Encrypt derives CLLW terms only, so no EQL block-ORE type is
   producible (stashgen refuses TextOrdOre and TextSearchOre — EQL stores block ORE terms and the engine derives CLLW ORE stack#1132).
3. Date, timestamp and decimal are OPE-only in cllw-ore.

Proposal

1. Plaintext layer: orderable-bytes (cipherstash/ore.rs, orderable-bytes has no variable-length encoding — text and bytes can't share the order layer ore.rs#94), plus
   canonicalisation:

   • floats as in vitaminc-prf: equality terms for the new kinds, floats and decimal, from one canonical form per kind #373;
   • timestamps truncated to microseconds;
   • text normalised to NFC, then accents and case folded (NFD, drop combining
     marks, Unicode default case folding), pinned to the same Unicode version
     as vitaminc-prf: equality terms for the new kinds, floats and decimal, from one canonical form per kind #373.

   Order terms fold where equality terms don't: a folded order term only
   produces ties, while a folded equality would match the wrong rows.

2. A Scheme trait with three implementations: block ORE (over ore-rs,
   at each kind's natural width, with no 8-byte padding), CLLW ORE and CLLW
   OPE (over cllw-ore).

3. Order terms derived from &Value, with one exhaustive match. Every
   orderable kind works under every scheme, except Bool, which gets no order
   terms. Block ORE for text waits for Tracking: review and release chained block ORE (ore v2) so text can use block ORE ore.rs#95 and is listed as
   an exception until then.

4. Prerequisite, in cipherstash-suite (which has Issues turned off):

   • put cllw-ore's typed impls behind a cargo feature that is on by default,
     so cipherstash-client's stored terms don't change;
   • add a bytes-level "encrypt these orderable bytes" entry point;
   • release a minor version.

Needs cipherstash/ore.rs#94, #372 and the cllw-ore release. Decided in ADR-0002
(cipherstash/stack#1139).

Relationship to other work

• stack-encrypt: every index is compiled into the core crate — move Equality, Match, Ore, Ope into their own crates stack#1063 plans ORE and OPE index crates in stack. They become
  thin wrappers over this crate.