settings ui: Create settings key trait (#37489)

This PR separates out the associated constant `KEY` from the `Settings`
trait into a new trait `SettingsKey`. This allows for the key trait to
be derived using attributes to specify the path so that the new
`SettingsUi` derive macro can use the same attributes to determine top
level settings paths thereby removing the need to duplicate the path in
both `Settings::KEY` and `#[settings_ui(path = "...")]`

Co-authored-by: Ben Kunkle <ben@zed.dev>

Release Notes:

- N/A

---------

Co-authored-by: Ben Kunkle <ben@zed.dev>

crates/editor/src/editor_settings.rs

@@ -6,7 +6,7 @@ use language::CursorShape;
 use project::project_settings::DiagnosticSeverity;
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use settings::{Settings, SettingsSources, SettingsUi, VsCodeSettings};
+use settings::{Settings, SettingsKey, SettingsSources, SettingsUi, VsCodeSettings};
 use util::serde::default_true;
 
 /// Imports from the VSCode settings at
@@ -431,8 +431,9 @@ pub enum SnippetSortOrder {
     None,
 }
 
-#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi)]
+#[derive(Clone, Default, Serialize, Deserialize, JsonSchema, SettingsUi, SettingsKey)]
 #[settings_ui(group = "Editor")]
+#[settings_key(None)]
 pub struct EditorSettingsContent {
     /// Whether the cursor blinks in the editor.
     ///
@@ -777,8 +778,6 @@ impl EditorSettings {
 }
 
 impl Settings for EditorSettings {
-    const KEY: Option<&'static str> = None;
-
     type FileContent = EditorSettingsContent;
 
     fn load(sources: SettingsSources<Self::FileContent>, _: &mut App) -> anyhow::Result<Self> {