Fix LocalFS stream listing

[trueleo]

Fixes #318 .

Description

Fix listing in local storage mode. Looks for .stream.json in the directory only then counts it as a valid stream candidate

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This PR has:

• been tested to ensure log ingestion and log query works.
• added comments explaining the "why" and the intent of the code wherever would not be obvious for an unfamiliar reader.
• added documentation for new or modified features or behaviors.