[BI-2914] Swap OU exref usages with brapi OU dbId

[jloux-brapi]

Description

Story: BI-2914

• Swapped exref usages on BI observation usages with brapi observation unit dbIds.
• Fixed some remaining trial and observation usages as well

Dependencies

Testing

Checklist:

• I have performed a self-review of my own code
• I have tested my code and ensured it meets the acceptance criteria of the story
• I have create/modified unit and/or integration tests to cover this change or tests are not applicable
• I have commented my code, particularly in hard-to-understand areas
• I have either updated the source of truth or arranged for update with product owner if needed https://breedinginsight.atlassian.net/wiki/spaces/BI/pages/1559953409/Source+of+Truth