Include document specific debug info (#16215)

## Summary

Related https://github.com/astral-sh/ruff-vscode/pull/692.

## Test Plan

**When there's no active text document:**

```
[Info  - 10:57:03 PM] Global:
executable = /Users/dhruv/work/astral/ruff/target/debug/ruff
version = 0.9.6
position_encoding = UTF16
workspace_root_folders = [
    "/Users/dhruv/playground/ruff",
]
indexed_configuration_files = [
    "/Users/dhruv/playground/ruff/pyproject.toml",
    "/Users/dhruv/playground/ruff/formatter/ruff.toml",
]
open_documents = 0
client_capabilities = ResolvedClientCapabilities {
    code_action_deferred_edit_resolution: true,
    apply_edit: true,
    document_changes: true,
    workspace_refresh: true,
    pull_diagnostics: true,
}

global_client_settings = ResolvedClientSettings {
    fix_all: true,
    organize_imports: true,
    lint_enable: true,
    disable_rule_comment_enable: true,
    fix_violation_enable: true,
    show_syntax_errors: true,
    editor_settings: ResolvedEditorSettings {
        configuration: None,
        lint_preview: None,
        format_preview: None,
        select: None,
        extend_select: None,
        ignore: None,
        exclude: None,
        line_length: None,
        configuration_preference: EditorFirst,
    },
}
```

**When there's an active text document that's been passed as param:**

```
[Info  - 10:53:33 PM] Global:
executable = /Users/dhruv/work/astral/ruff/target/debug/ruff
version = 0.9.6
position_encoding = UTF16
workspace_root_folders = [
    "/Users/dhruv/playground/ruff",
]
indexed_configuration_files = [
    "/Users/dhruv/playground/ruff/pyproject.toml",
    "/Users/dhruv/playground/ruff/formatter/ruff.toml",
]
open_documents = 1
client_capabilities = ResolvedClientCapabilities {
    code_action_deferred_edit_resolution: true,
    apply_edit: true,
    document_changes: true,
    workspace_refresh: true,
    pull_diagnostics: true,
}

Document:
uri = file:///Users/dhruv/playground/ruff/lsp/play.py
kind = Text
version = 1
client_settings = ResolvedClientSettings {
    fix_all: true,
    organize_imports: true,
    lint_enable: true,
    disable_rule_comment_enable: true,
    fix_violation_enable: true,
    show_syntax_errors: true,
    editor_settings: ResolvedEditorSettings {
        configuration: None,
        lint_preview: None,
        format_preview: None,
        select: None,
        extend_select: None,
        ignore: None,
        exclude: None,
        line_length: None,
        configuration_preference: EditorFirst,
    },
}
config_path = Some("/Users/dhruv/playground/ruff/pyproject.toml")

...
```

Replace `...` at the end with the output of `ruff check --show-settings
path.py`

crates/ruff_server/src/session/index.rs

@@ -177,21 +177,6 @@ impl Index {
             .register_workspace(&Workspace::new(url), global_settings)
     }
 
-    pub(super) fn num_documents(&self) -> usize {
-        self.documents.len()
-    }
-
-    pub(super) fn num_workspaces(&self) -> usize {
-        self.settings.len()
-    }
-
-    pub(super) fn list_config_files(&self) -> Vec<&Path> {
-        self.settings
-            .values()
-            .flat_map(|WorkspaceSettings { ruff_settings, .. }| ruff_settings.list_files())
-            .collect()
-    }
-
     pub(super) fn close_workspace_folder(&mut self, workspace_url: &Url) -> crate::Result<()> {
         let workspace_path = workspace_url.to_file_path().map_err(|()| {
             anyhow!("Failed to convert workspace URL to file path: {workspace_url}")
@@ -404,6 +389,23 @@ impl Index {
             .next_back()
             .map(|(_, settings)| settings)
     }
+
+    /// Returns an iterator over the workspace root folders contained in this index.
+    pub(super) fn workspace_root_folders(&self) -> impl Iterator<Item = &Path> {
+        self.settings.keys().map(PathBuf::as_path)
+    }
+
+    /// Returns the number of open documents.
+    pub(super) fn open_documents_len(&self) -> usize {
+        self.documents.len()
+    }
+
+    /// Returns an iterator over the paths to the configuration files in the index.
+    pub(super) fn config_file_paths(&self) -> impl Iterator<Item = &Path> {
+        self.settings
+            .values()
+            .flat_map(|WorkspaceSettings { ruff_settings, .. }| ruff_settings.config_file_paths())
+    }
 }
 
 /// Maps a workspace folder root to its settings.

crates/ruff_server/src/session/index/ruff_settings.rs

@@ -20,6 +20,7 @@ use ruff_workspace::{
 
 use crate::session::settings::{ConfigurationPreference, ResolvedEditorSettings};
 
+#[derive(Debug)]
 pub struct RuffSettings {
     /// The path to this configuration file, used for debugging.
     /// The default fallback configuration does not have a file path.
@@ -28,6 +29,12 @@ pub struct RuffSettings {
     settings: Settings,
 }
 
+impl RuffSettings {
+    pub(crate) fn path(&self) -> Option<&Path> {
+        self.path.as_deref()
+    }
+}
+
 impl Deref for RuffSettings {
     type Target = Settings;
 
@@ -298,15 +305,16 @@ impl RuffSettingsIndex {
             .clone()
     }
 
-    pub(crate) fn list_files(&self) -> impl Iterator<Item = &Path> {
+    pub(super) fn fallback(&self) -> Arc<RuffSettings> {
+        self.fallback.clone()
+    }
+
+    /// Returns an iterator over the paths to the configuration files in the index.
+    pub(crate) fn config_file_paths(&self) -> impl Iterator<Item = &Path> {
         self.index
             .values()
             .filter_map(|settings| settings.path.as_deref())
     }
-
-    pub(super) fn fallback(&self) -> Arc<RuffSettings> {
-        self.fallback.clone()
-    }
 }
 
 struct EditorConfigurationTransformer<'a>(&'a ResolvedEditorSettings, &'a Path);