Make PopulateData lib usage explicit to deal with autoloading issues

[danguita]

Connects to #140.

What does this PR do?

This is is likely a class autoloading problem in staging/production. Even when everything under /app is autoloaded in development and eager loaded in staging/production, I'd keep this library out of the app context so we're making the PopulateData::Gobierto class usage explicit. It is now needed to require "populate_data" when making use of that library.

How should this be manually tested?

Ensure that the PopulateData::Gobierto is properly loaded from GobiertoAdmin::GobiertoBudgetConsultations::BudgetLineCollectionBuilder in an eager loaded environment config such as staging or production.

It is only used in the Consultation Item management action so let's check this form still works:

http:https://gobierto.dev/admin/budgets/consultations/<consultation_id>/items/<consultation_item_id>/edit.

[ferblape]

Let´s try it in staging. Thank you!

[danguita]

Thanks man! 🙌

[ferblape]

It works!