Fixes #1180

If a user is in more than 100 studies as an admin or a user, the Studies page will fail to load for that user, giving a validation error from DynamoDB BatchGetItem in the returned JSON. From what I understand, the first query which finds which studies a user has access to, succeeds. Only the fetch of the details for these studies fails.

Description of changes:

This enables chunking of DynamoDB BatchGet requests if there are more than 100 results. I'm not sure if this is the most appropriate solution as I think a Scan should be used, but it was a quick fix for our SWB deployment.

Checklist:

• Have you successfully deployed to an AWS account with your changes?
• Have you written new tests for your core changes, as applicable?
• Have you successfully tested with your changes locally?
• If new dependencies have been added, have they been pinned to specific versions?
• Is this change also required on the AWS Solution version?
• Have you updated openapi.yaml if you made updates to API definition (including add, delete or update parameter and request data schema)?
• If you had to run manual tests, have you considered automating those tests by adding them to end-to-end tests?
• If you are updating the changelog and vending out a new release, have you updated versionNumber and versionDate in .defaults.yml

AS review ticket id:

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