2344 add support for multi get operation in the database

[netrome]

Draft PR for early feedback. I'm a bit torn regarding the boxed iterators. While they are a bit more ergonomic and flexible as opposed to working directly with slices/vecs, it's also very verbose and I'm also worried about all the levels of boxing hurting performance.

EDIT: Rewritten to not modify the StorageInspect trait after feedback in Slack.
Note that the VM changes aren't visible in this PR. I will open a separate PR for them, but for reference this is how the StorageInspect trait is assumed to be extended in the current version:

Linked Issues/PRs

Closes #2344

Description

This PR extends the KeyValueInspect trait using Boxed iterators.

Checklist

• Breaking changes are clearly marked as such in the PR description and changelog
• New behavior is reflected in tests
• The specification matches the implemented behavior (link update PR if changes are needed)

Before requesting review

• I have reviewed the code myself
• I have created follow-up issues caused by this PR and linked them here