fix(EMS-3508): no pdf - application submission - XLSX - buyer conditions

[ttbarnes]

Introduction ✏️

This PR fixes an issue with the XLSX where the formatting index for the "declarations" title be incorrect due to a missing buyer condition.

Resolution ✔️

• Update XLSX_ROW_INDEXES to:
  • Increment 2x titles if exporterIsConnectedWithBuyer is true.
  • Increment 2x titles if totalContractValueOverThreshold and exporterHasPreviousCreditInsuranceWithBuyer are true.
  • Increment AGENT_ADDRESS if totalContractValueOverThreshold` is true.
• Update API test mocks.

Miscellaneous ➕

• Add E2E tests for submitting an application (single and multiple contracts) with minimal buyer conditions.