feat: Add pre_extraction_item_counts to EventData for sync duration estimation

[i-arnavra3]

Description

Adds an optional pre_extraction_item_counts field to EventData so ADaaS snap-ins can report per-record-type counts on the MetadataExtractionDone event. Adds the ItemTypeCount interface and ItemInputType enum (main or users) and exports both. The field is optional, so existing snap-ins are unaffected.

Design doc: ADaaS estimated duration extension

Connected Issues

ASFND-360

Checklist

• Tests added/updated and ran with npm run test OR no tests needed.
• Ran backwards compatibility tests with npm run test:backwards-compatibility.
• Code formatted and checked with npm run lint.
• Tested airdrop-template linked to this PR.
• Documentation updated and provided a link to PR / new docs OR no docs needed.

[Aakkash-Suresh]

LGTM

[gasperzgonec]

This was tested with the airdrop-template, and it returns this during the METADATA_EXTRACTION_DONE, which seems correct.

  event_data: {
    pre_extraction_item_counts: [
      {
        record_type: 'todos',
        count: 15,
        model_input_type: 'main'
      },
      {
        record_type: 'users',
        count: 10,
        model_input_type: 'users'
      }
    ],
    artifacts: [
      {
        id: 'don:core:dvrv-us-1:devo/1smXA7GSnn:artifact/97012',
        item_type: 'external_domain_metadata',
        item_count: 1
      }
    ]
  },

No errors or warnings, so platform seems to be accepting this on the QA.

This, however, still fails on PROD (METADATA_EXTRACTION_ERROR) with the following message: Invalid field: pre_extraction_item_counts.

[gasperzgonec]

This has been promoted to PROD environment and should be ready to be promoted in the SDK as well.