Create "happy path" project fixture and use it for tests/functional/list/test_list.py

[QMalcolm]

Housekeeping

• I am a maintainer of dbt-core

Short description

When we write functional tests we generally end up writing more fixtures. A lot of these fixtures we write are either duplicates of fixtures for other functional tests that already exist (or are very close copies). Additionally because we don't have a standard "happy path" fixture, it has happened a few times that test which checks specific functionality fails to detect that it is broken when a certain type of node is involved because it wasn't included in the project fixture. By creating a happy path project fixture we solve both issues. Tests should try to use existing nodes in the happy path fixture, and when they cannot, add a new node to it (so all tests get it). Additionally because the happy path fixture will be broad, it should help guarantee node types existing don't break certain functionalities.

Acceptance criteria

• There exists a happy_path_project fixture for our functional tests
• We use it for tests in tests/functional/list/test_list.py