Replace ds.Query interface with lower-level Iterator interface

[jsimnz]

Currently we use the ds.Query interface in several places, when really, we only need the general Iterator interfaces provided by most KV stores.

This will likely require a much more foundational refactor to Defra to replace the general ds.Datastore interfaces, with native abstractions that are designed to expose Iterators instead of Queries.

The reason we need to replace the ds.Query system, is that its basically just a very bad implementation of our query planner engine, as it supports complex ordering, filtering, and more. But, if we look at the call sites of where we use the Query system, all we need is an iterator. Whats worse, is that those call sites, like in the fetcher, need to access common Iterator methods, like Seek which Query doesn't provide.

Update 2024-12-16

A new repo CoreKV has been created by John, this contains a new stuff to replace most of the Defra datastore package, it exposes Seek functionality.

This ticket will now integrate that library into Defra.

[jsimnz]

Closed #1600 due to it being a duplicate. Context from that thread:

Follow up refactor for #490 and #1500.

[AndrewSisley]

Blocked by sourcenetwork/corekv#14

WIP branch name 1813-integrate-ckv