dbt_project.yml log-path respects project directory

[MichelleArk]

Resolves: #6957

Fixes log_path setting in flags to respect project_dir, if available

On before_click_merge branch

❯ dbt run --project-dir ~/src/jaffle_shop
...
❯ ls logs
ls: logs: No such file or directory
❯ ls ~/src/jaffle_shop/logs
dbt.log

currently, on main

❯ dbt run --project-dir ~/src/jaffle_shop
...
❯ ls logs
dbt.log #bad!
❯ ls ~/src/jaffle_shop/logs
ls: /Users/michelleark/src/jaffle_shop/logs: No such file or directory #also bad!

🎩 after fix:

❯ dbt run --project-dir ~/src/jaffle_shop
...
❯ ls logs
ls: logs: No such file or directory
❯ ls ~/src/jaffle_shop/logs
dbt.log

Description

Checklist

• I have read the contributing guide and understand what's expected of me
• I have signed the CLA
• I have run this code in development and it appears to resolve the stated issue
• This PR includes tests, or tests are not required/relevant for this PR
• I have opened an issue to add/update docs, or docs changes are not required/relevant for this PR
• I have run changie new to create a changelog entry

[github-actions]

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[MichelleArk]

Removing the fix to tests/functional/partial_parsing/test_pp_vars.py::TestProfileEnvVars in favor of #6916. Scope of this PR is now just the difference in behaviour with log-path between click and legacy cli.

[aranke]

LGTM, resolved questions offline.