Added new attribute preselectVariableId so we can take note of it when the form is being submitted

GCP-10043

Reviewer: Daniel Villafuerte
Added code to make the preselectVariableId dynamic and reflect the correct value ONLY if it came from a popup (only being use by ETL when updating variable)

GCP-10043

Reviewer: Daniel Villafuerte
Added Unit test cases to take note if the preselectVariableId is being carried over to the model attribute if the form is from a popup or not

GCP-10043

Reviewer: Daniel Villafuerte
Cleanup code, adde curly braces to if/else condition and return empty array instead of null for functions

GCP-10043

Reviewer: Daniel Villafuerte