feat(tiering): Experimental list node tiering

[mkaruza]

Decoupline QList from TieredStorage implementation details via
TieringParams structure callbacks.

• Introduce TieringParams struct holding function callbacks and offload state
• Add Node::Upload() to restore an externally-loaded node back into memory
• Add QList::SetDbIndex() to handle db reassignment, materializing offloaded
  nodes when tiering is active
• Add StashListNode / ReadTieredListNode in TieredStorage
• Add tiered_storage_test.cc coverage for list node offload/reload lifecycle
• Add tiering_test.py integration tests for list tiering behavior

[augmentcode]

🤖 Augment PR Summary

Summary: This PR adds experimental tiered-storage support for QList nodes (quicklist v2) and expands test coverage around list node offload/onload/delete.

Changes:

• Wire QList::TieringParams callbacks in list_family.cc to stash, load, and delete individual list nodes via TieredStorage.
• Extend DB flush logic to explicitly clear QL2 lists so any offloaded nodes are cleaned up from tiered storage.
• Add a new ListNodeTieringTest suite exercising stash/load/delete/rename/expire/flushall behaviors with tiered list nodes.
• Add a Python integration test validating replication + RDB load correctness when tiered list nodes exist on the master.
• Introduce/declare flags needed by the new tests (experimental list support + list tiering thresholds/compression knobs).

Technical Notes: The list-node offload path stashes node fragments independently from the top-level key, so cleanup and replication tests focus on mixed pending/offloaded states and correctness after materialization.

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[augmentcode]

Review completed. 2 suggestions posted.

Comment augment review to trigger a new review at any time.

[Copilot]

Pull request overview

This PR adds experimental tiered-storage support for QList::Node objects, wiring list node offload/onload/delete callbacks into the list implementation and extending tiered storage’s ID/addressing to support non-key-backed fragments.

Changes:

• Extend tiered-storage identifiers and op-manager bookkeeping to support list-node fragments (ListNodeId, ReadId).
• Implement list-node decoding/upload and integrate list tiering callbacks into list command codepaths.
• Add C++ and Python tests covering list node offload/onload plus replication with tiered lists.

Reviewed changes

Copilot reviewed 18 out of 18 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
tests/dragonfly/tiering_test.py	Adds a replication test that exercises tiered list objects.
src/server/tiering/op_manager.h	Extends OwnedEntryId to include list-node identifiers.
src/server/tiering/op_manager.cc	Adds ownership/stringification support for list-node IDs.
src/server/tiering/decoders.h	Generalizes Decoder::Upload to void* and adds ListNodeDecoder.
src/server/tiering/decoders.cc	Implements ListNodeDecoder and updates existing decoders to new Upload signature.
src/server/tiering/common.h	Adds ListNodeId + ReadId variants for list-node reads.
src/server/tiered_storage.h	Introduces ReadId, splits prime vs partial stashing APIs, adds list-node read/stash helpers and IsClosed().
src/server/tiered_storage.cc	Implements list-node stash/upload/delete paths and adds experimental list-tiering flag.
src/server/tiered_storage_test.cc	Adds ListNodeTieringTest suite covering stash/load/delete/rename/expire/flush/move scenarios.
src/server/list_family.cc	Wires QList::TieringParams callbacks to tiered storage and tracks list DB index for node IDs.
src/server/hset_family.cc	Updates tiered read callsites to new ReadId API.
src/server/generic_family.cc	Ensures moved QList updates its DB index (materializing offloaded nodes if needed).
src/server/db_slice.cc	Updates cancel-stash callsites for new API and clears QLists during DB flush to release tiered list-node segments.
src/core/tiering_types.h	Adds FragmentRef::MallocUsed() API needed for stats updates.
src/core/tiering_types.cc	Implements MallocUsed() for CompactValue and QList::Node fragments.
src/core/qlist.h	Adds tiering callback params, DB index tracking, and node upload API for tiered restore.
src/core/qlist.cc	Implements node upload, callback-based cleanup/load/offload integration, and SetDbIndex() behavior.
src/core/qlist_test.cc	Removes the older minimal tiering unit test.

[Copilot]

If ReadTieredListNode() fails, the node likely remains offloaded (node->entry still not materialized) but the list operation will continue after only logging a warning; this can violate QList::Materialize() expectations and lead to crashes/corruption. Consider making load failures fatal (DFATAL) or ensuring the node is put into a safe in-memory state before returning (and/or propagate an error back to the command).

Suggested change

	if (!res) {
	LOG(WARNING) << "Failed to load list node from tiered storage: " << res.error().message();
	}
	CHECK(res) << "Failed to load list node from tiered storage: " << res.error().message();