Collect errors while building up the settings index

[dhruvmanila]

Summary

Related to astral-sh/ruff-vscode#571, this PR updates the settings index builder to trace all the errors it encountered. Without this, there's no way for user to know that something failed and some of the capability might not work as expected. For example, in the linked PR, the settings were invalid which means notebooks weren't included and there were no log messages for it.

Test Plan

Create an invalid ruff.toml file:

[tool.ruff]
extend-exclude = ["*.ipynb"]

Logs:

2024-08-12 18:33:09.873 [info] [Trace - 6:33:09 PM]   12.217043000s ERROR ruff:main ruff_server::session::index::ruff_settings: Failed to parse /Users/dhruv/playground/ruff/pyproject.toml

Notification Preview:

Another way to trigger is to provide an invalid cache-dir value:

[tool.ruff]
cache-dir = "$UNKNOWN"

Same notification preview but different log message:

2024-08-12 18:41:37.571 [info] [Trace - 6:41:37 PM]   21.700112208s ERROR ThreadId(30) ruff_server::session::index::ruff_settings: Error while resolving settings from /Users/dhruv/playground/ruff/pyproject.toml: Invalid `cache-dir` value: error looking key 'UNKNOWN' up: environment variable not found

With multiple pyproject.toml file:

2024-08-12 18:41:15.887 [info] [Trace - 6:41:15 PM]    0.016636833s ERROR ThreadId(04) ruff_server::session::index::ruff_settings: Error while resolving settings from /Users/dhruv/playground/ruff/pyproject.toml: Invalid `cache-dir` value: error looking key 'UNKNOWN' up: environment variable not found

2024-08-12 18:41:15.888 [info] [Trace - 6:41:15 PM]    0.017378833s ERROR ThreadId(13) ruff_server::session::index::ruff_settings: Failed to parse /Users/dhruv/playground/ruff/tools/pyproject.toml

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

[codspeed-hq]

CodSpeed Performance Report

Merging #12781 will not alter performance

_{Comparing dhruv/settings-index-error (2004c6a) with main (2ea7957)}

Summary

✅ 32 untouched benchmarks

[MichaReiser]

Thanks. This is a great addition!