Read user configuration from ~/.config/ruff/ruff.toml on macOS

[charliermarsh]

Summary

This PR moves Ruff's user-specific configuration from ~/Library/Application Support/ruff/ruff.toml to ~/.config/ruff/ruff.toml.

Many other tools do this. On my machine alone: dagger, zed, gatsby, gh, wandb, etc.

I also polled Twitter and it won in a landslide:

Let's ship this in v0.5.0, along with a deprecation warning (so we'll continue to respect ~/Library/Application Support/ruff/ruff.toml, but log a warning).

Closes #10739.

Test Plan

• Created a file with an unused import.
• Ran cargo check foo.py.
• Verified that the deprecated configuration was loaded and respected, with a warning:

warning: Reading configuration from `~/Library/Application Support` is deprecated. Please move your configuration to `/Users/crmarsh/.config/ruff/ruff/ruff.toml`.
[2024-04-23][16:09:10][ruff::resolve][DEBUG] Using configuration file (via cwd) at: /Users/crmarsh/Library/Application Support/ruff/ruff.toml

• Created ~/.config/ruff/ruff.toml.
• Verified that the new configuration was loaded:

[2024-04-23][16:10:23][ruff::resolve][DEBUG] Using configuration file (via cwd) at: /Users/crmarsh/.config/ruff/ruff.toml

[charliermarsh]

@konstin suggested this crate, and it does what we want across Windows and Linux / macOS, but open to other suggestions.

[charliermarsh]

We can remove dirs in a future release, but it stays around for now for backwards compatibility.

[github-actions]

ruff-ecosystem results

Linter (stable)

✅ ecosystem check detected no linter changes.

Linter (preview)

✅ ecosystem check detected no linter changes.

Formatter (stable)

✅ ecosystem check detected no format changes.

Formatter (preview)

✅ ecosystem check detected no format changes.

[MichaReiser]

Sooo, we're doing twitter driven development now 😂

[konstin]

I would change the reasoning/description: Follow the XDG specification on all Unix platforms. Ruff will now use the XDG config directory to read user-level configuration (default: ~/.config/ruff/ruff.toml) over Library/Application Support/ruff/ruff.toml on macOS.