[CT-2970] [Regression] Fix path: selector with --project-dir for dbt list

[jtcohen6]

Housekeeping

• I am a maintainer of dbt-core

Short description

The hopeful end of a brief saga:

• We fixed [CT-2665] [Regression] For the list command the path selector does not respect the --project-dir param #7819 for all commands
• Then we adjusted the fix to use a context manager (Use events.contextvar because of multiprocessing unable to pickle ContextVar #7949)
• That preserved the fix for all commands except list, which doesn't use the context manager because it doesn't inherit from RunnableTask

Acceptance criteria

I can run this from outside the root directory of my dbt project:

$ dbt -q ls -s path:models/my_model.sql --project-dir my_dbt_project/
my_dbt_project.my_model

Impact to Adapters

zero impact

Context

#7819 (comment)