[pierugo-dfinity]

• In the certification pool, stop erasing the type of unvalidated_{share/cert}_index and split unvalidated into shares and full certs, both to leverage the type system more and avoid potential bugs (f.ex. we remove a panic).
• Make HeightIndex::remove_all_below return the removed artifacts: this simplify and improves the performance of both consensus' purge_below and certification's remove_all_unvalidated_below by avoiding an additional iteration.
• Instead of providing HeightIndex::heights, provide min_height and max_height, since this is only what the production callers care for. It avoids iterating and sometimes collecting.
• Move CertificationPoolImpl::all_heights_with_artifacts to test-only and remove it from the trait since it was not used in production.
• Misc: avoid some clones and stop allocating into vectors in a few places inside inmemory_pool.rs and lmdb_pool.rs (i.e. consensus pools).

[Copilot]

🟢 Approval recommended

The focused refactor preserves hashing, index consistency, ordering, and purge boundaries, with no blocking issues identified.

No open issues 🎉

What changed in this PR

This PR reduces allocation, cloning, and height-scanning overhead in the certification and in-memory consensus pools while simplifying their internal APIs.

Changes:

• Purge indexed artifacts below a height directly and streamline range queries.
• Store unvalidated certifications and shares in separate, typed maps.
• Move the artifact-height helper out of the public interface and into test-only code, updating consistency assertions.

File	Description
rs/​interfaces/​src/​certification.rs	Removes the artifact-height helper from the public pool trait.
rs/​artifact_pool/​src/​inmemory_pool.rs	Streamlines purging, artifact retrieval, and height queries.
rs/​artifact_pool/​src/​height_index.rs	Adds draining purge iteration and direct height-bound accessors.
rs/​artifact_pool/​src/​certification_pool.rs	Splits unvalidated storage by artifact type and updates tests.

_{Review effort: Balanced}