settings: Use a derive macro for refine (#38451)

When we refactored settings to not pass JSON blobs around, we ended up
needing
to write *a lot* of code that just merged things (like json merge used
to do).

Use a derive macro to prevent typos in this logic.

Release Notes:

- N/A

crates/repl/src/jupyter_settings.rs

@@ -19,19 +19,10 @@ impl JupyterSettings {
 }
 
 impl Settings for JupyterSettings {
-    fn from_defaults(content: &settings::SettingsContent, _cx: &mut App) -> Self {
+    fn from_settings(content: &settings::SettingsContent, _cx: &mut App) -> Self {
         let jupyter = content.editor.jupyter.clone().unwrap();
         Self {
             kernel_selections: jupyter.kernel_selections.unwrap_or_default(),
         }
     }
-
-    fn refine(&mut self, content: &settings::SettingsContent, _cx: &mut App) {
-        let Some(jupyter) = content.editor.jupyter.as_ref() else {
-            return;
-        };
-        if let Some(kernel_selections) = jupyter.kernel_selections.clone() {
-            self.kernel_selections.extend(kernel_selections)
-        }
-    }
 }

crates/repl/src/repl_settings.rs

@@ -1,6 +1,5 @@
 use gpui::App;
 use settings::Settings;
-use util::MergeFrom;
 
 /// Settings for configuring REPL display and behavior.
 #[derive(Clone, Debug)]
@@ -18,7 +17,7 @@ pub struct ReplSettings {
 }
 
 impl Settings for ReplSettings {
-    fn from_defaults(content: &settings::SettingsContent, _cx: &mut App) -> Self {
+    fn from_settings(content: &settings::SettingsContent, _cx: &mut App) -> Self {
         let repl = content.repl.as_ref().unwrap();
 
         Self {
@@ -26,13 +25,4 @@ impl Settings for ReplSettings {
             max_columns: repl.max_columns.unwrap(),
         }
     }
-
-    fn refine(&mut self, content: &settings::SettingsContent, _cx: &mut App) {
-        let Some(repl) = content.repl.as_ref() else {
-            return;
-        };
-
-        self.max_columns.merge_from(&repl.max_columns);
-        self.max_lines.merge_from(&repl.max_lines);
-    }
 }