Expose environment variables and dbt vars configuration via ProjectConfig

[tatiana]

Context

As of Cosmos 1.2.4, users cannot define dbt --vars when running LoadMode.DBT_LS during project parsing / DAG rendering. They are able to define environment variables, thanks to #690 .

At the moment, users have to also define the environment variables and dbt vars for the task execution, using:
operator_args={"env": ..., "var": ...}
as described in https://astronomer.github.io/astronomer-cosmos/configuration/operator-args.html

This discussion started as part of this review:
#690 (review)

Acceptance criteria

• Deprecate operator args env & var, raising warnings, and fully deprecate them as of Cosmos 2.x
• Deprecate RenderConfig.env_vars, raising warnings, and fully deprecate them as of Cosmos 2.x
• Expose both dbt_vars and env_vars within the ProjectConfig
• Update the documentation and example DAGs to use the new ProjectConfig arguments

[dosubot]

🤖

It seems like you've got this under control, if you want help or have specific questions, let me know what I can do for you!

[jbandoro]

Thanks @tatiana for the detailed AC, I can work on contributing this 👍

[jbandoro]

@tatiana do you by chance have a dbt example where dbt variables passed to dbt ls will change the models listed. I'd like to have tests for this when use load method of dbt ls with --vars but haven't found any examples of where variables could be used in order to change models listed, and consequently the dbt graph cosmos would render.

edit: I found a dbt issue here, where the reference uses a variable - will give this a go!