feat: run dbt in batches for document_metadata model

[njuguna-n]

Description

If start_timestamp and batch_size variables are set then run updates to the document_metadata model in batches.

This PR depends on this corresponding PR in the CHT Sync repository.

medic/cht-sync#156

Code review checklist

• Readable: Concise, well named, follows the style guide, documented if necessary.
• Documented: Configuration and user documentation on cht-docs
• Tested: Unit and/or e2e where appropriate
• Backwards compatible: Works with existing data and configuration or includes a migration. Any breaking changes documented in the release notes.

License

The software is provided under AGPL-3.0. Contributions to this project are accepted under the same license.