Add clarification on which database variable takes precedence if set in diff locations

### Contributions

- [X] I have read the contribution docs, and understand what's expected of me.

### Link to the page on docs.getdbt.com requiring updates

User reached out to support asking for clarity on the order in which dbt will use the 'database' variable if it is set at multiple different places?

### What part(s) of the page would you like to see updated

User would like clarity regarding which variable takes precedence. It appears that in the IDE, the dbt_project.yml takes precedence over individual user credentials. Whereas when running a job, the environment takes precedence over the dbt_project.yml. Is this correct? And if so, do you have any documentation regarding the exact order of precedence depending on where the variable is set as there is very little regarding this in the current docs?

Content could live in following pages:
- https://docs.getdbt.com/reference/dbt_project.yml
- https://docs.getdbt.com/docs/collaborate/environments/dbt-cloud-environments
- Environments faq: https://docs.getdbt.com/faqs/Environments/beta-release
- Warehouse faq: https://docs.getdbt.com/faqs/Warehouse/bq-impersonate-service-account-setup
- Project faq: https://docs.getdbt.com/faqs/Project/consolidate-projects

### Additional information

Zendesk ticket: 43438