[BI-2803] Create new obsVarCount stat for both Experiment creation and appends use case

[jloux-brapi]

Description

Story: BI-2803

• Added a new stat obsVarCount for the frontend to use to display the number of observations in an experiment import preview
• Update the experiment creation and appends workflow to update the stat

Dependencies

bi-web PR

Testing

Prerequisites

To test, you will want to try creating a program from scratch, and complete a germplasm and ontology upload. You will need to reference the ontology terms you created as "observation variables" during the testing.

Tests

• Verify Observation Variable count is correct in the preview in multiple use cases in the Experiment Import Creation workflow:
• • No obs vars
• • Singular obs vars
• • Multiple obs vars
• Verify Observation Variable count is correct in the preview in multiple use cases in the Experiment Import Appends workflow, for both top-level and sub-entity dataset appends:
• • No obs vars
• • Singular obs vars
• • Multiple obs vars

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