[#384] Reorganize exports by named exports - agents-hosting-storage

[ceciliaavila]

Addresses #384

Description

This PR removes from the public API classes and methods that should be private because they are intended for internal use.

NOTE:
This PR introduces breaking changes, as previously public members are now inaccessible.

Detailed Changes

• agents-hosting-storage-blob
  • Removed export clause in maybeCast function.
  • Prevented the export of the sanitizeBlobKey function by implementing selective exports in blobsTranscriptStore.ts.
• agents-hosting-storage-cosmos
  • Made initialize function private as it's intended for internal use only.
  • Avoided exporting the DoOnce class by selectively exporting members in cosmosDbPartitionedStorage.ts.
• Updated API docs to reflect the changes.

Testing

These images show two samples working. One using BlobStorage as transcriptMiddleware and the other using CosmosDb as the application storage.