EQL: write the same SQL out as eql_v3 and eql_v4, so Stack Encrypt columns are their own Postgres types #1141

Background

EQL's SQL installs data types (domains such as eql_v3_text_eq, kept in the
public schema) and the functions that compare them (in the disposable
eql_v3 and eql_v3_internal schemas, per ADR-0001). Each domain checks the
payload's version field: VALUE->>'v' = '3'.

Problem

Stack Encrypt and cipherstash-client both write the same eql_v3_* domains,
but their search terms never match each other. A Go query against a column
the TypeScript SDK wrote returns no rows, and nothing warns. ADR-0002 (#1139)
separates them as EQL v4: identical SQL, but distinct Postgres types, so a
mismatched query fails when it is planned.

Proposal

1. Replace the literal schema name and version in the hand-written
   packages/eql/src/v3/** SQL with build-time placeholders, as eql-codegen's
   templates already do ({{ schema }}). This covers about 24k lines that
   mention eql_v3, and VALUE->>'v' = '3' in every domain check.
2. Have the build write out eql_v3 (version 3) and eql_v4 (version 4),
   each with its own release manifest and digests.
3. Keep ADR-0001's split: public.eql_v4_* data domains survive reinstall,
   and eql_v4 and eql_v4_internal stay disposable.
4. Run the SQLx suites against both. Add a test that an eql_v4 query term
   can't be compared with an eql_v3 column.

This can start now; it depends on nothing in vitaminc.