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/dap/src/debugger_settings.rs

@@ -2,7 +2,7 @@ use dap_types::SteppingGranularity;
 use gpui::{App, Global};
 use schemars::JsonSchema;
 use serde::{Deserialize, Serialize};
-use settings::{Settings, SettingsSources, SettingsUi};
+use settings::{Settings, SettingsKey, SettingsSources, SettingsUi};
 
 #[derive(Copy, Clone, Debug, Serialize, Deserialize, JsonSchema, PartialEq, Eq, SettingsUi)]
 #[serde(rename_all = "snake_case")]
@@ -12,11 +12,12 @@ pub enum DebugPanelDockPosition {
     Right,
 }
 
-#[derive(Serialize, Deserialize, JsonSchema, Clone, Copy, SettingsUi)]
+#[derive(Serialize, Deserialize, JsonSchema, Clone, Copy, SettingsUi, SettingsKey)]
 #[serde(default)]
 // todo(settings_ui) @ben: I'm pretty sure not having the fields be optional here is a bug,
 // it means the defaults will override previously set values if a single key is missing
-#[settings_ui(group = "Debugger", path = "debugger")]
+#[settings_ui(group = "Debugger")]
+#[settings_key(key = "debugger")]
 pub struct DebuggerSettings {
     /// Determines the stepping granularity.
     ///
@@ -64,8 +65,6 @@ impl Default for DebuggerSettings {
 }
 
 impl Settings for DebuggerSettings {
-    const KEY: Option<&'static str> = Some("debugger");
-
     type FileContent = Self;
 
     fn load(sources: SettingsSources<Self::FileContent>, _: &mut App) -> anyhow::Result<Self> {