feat: support iterable for druid lookups-cached-single extension

[TessaIO]

Relates to #15936.

Description

This PR aims to change the behavior of the druid lookups-cached-single extension. In fact, we aim to introduce the option to iterate over fetched data from the dataFetcher. We need this in the case of loadingLookups, that's why these changes don't impact the pollingLookup feature.
I also added the handling of a use case where the data exists in Druid but not in the actual data fetcher, which is in our use-case JDBC Data fetcher.

Release note

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Key changed/added classes in this PR

• Support iterating over fetched data for the loadinglookups for the druid lookups-cached-single extension

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This PR has:

• been self-reviewed.
• added documentation for new or modified features or behaviors.
• a release note entry in the PR description.
• added Javadocs for most classes and all non-trivial methods. Linked related entities via Javadoc links.
• added or updated version, license, or notice information in licenses.yaml
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added unit tests or modified existing tests to cover new code paths, ensuring the threshold for code coverage is met.
• added integration tests.
• been tested in a test Druid cluster.

[TessaIO]

ping @cryptoe. Can you also drop a quick review on this?

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