Use real file path when available in ruff server

[charliermarsh]

Summary

As-is, we're using the URL path for all files, leading us to use paths like:

/c%3A/Users/crmar/workspace/fastapi/tests/main.py

This doesn't match against per-file ignores and other patterns in Ruff configuration.

This PR modifies the LSP to use the real file path if available, and the virtual file path if not.

Closes #11751.

Test Plan

Ran the LSP on Windows. In the FastAPI repo, added:

[tool.ruff.lint.per-file-ignores]
"tests/**/*.py" = ["F401"]

And verified that an unused import was ignored in tests after this change, but not before.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.