chore: Remove a bunch of unused structs (#16139)

Found by beta clippy.

Release Notes:

- N/A

crates/gpui/src/elements/list.rs

@@ -158,12 +158,6 @@ struct ListItemSummary {
 #[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
 struct Count(usize);
 
-#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-struct RenderedCount(usize);
-
-#[derive(Clone, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-struct UnrenderedCount(usize);
-
 #[derive(Clone, Debug, Default)]
 struct Height(Pixels);
 
@@ -904,18 +898,6 @@ impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Count {
     }
 }
 
-impl<'a> sum_tree::Dimension<'a, ListItemSummary> for RenderedCount {
-    fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
-        self.0 += summary.rendered_count;
-    }
-}
-
-impl<'a> sum_tree::Dimension<'a, ListItemSummary> for UnrenderedCount {
-    fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
-        self.0 += summary.unrendered_count;
-    }
-}
-
 impl<'a> sum_tree::Dimension<'a, ListItemSummary> for Height {
     fn add_summary(&mut self, summary: &'a ListItemSummary, _: &()) {
         self.0 += summary.height;

crates/notifications/src/notification_store.rs

@@ -68,9 +68,6 @@ pub struct NotificationSummary {
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
 struct Count(usize);
 
-#[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
-struct UnreadCount(usize);
-
 #[derive(Clone, Copy, Debug, Default, PartialEq, Eq, PartialOrd, Ord)]
 struct NotificationId(u64);
 
@@ -491,12 +488,6 @@ impl<'a> sum_tree::Dimension<'a, NotificationSummary> for Count {
     }
 }
 
-impl<'a> sum_tree::Dimension<'a, NotificationSummary> for UnreadCount {
-    fn add_summary(&mut self, summary: &NotificationSummary, _: &()) {
-        self.0 += summary.unread_count;
-    }
-}
-
 struct AddNotificationsOptions {
     is_new: bool,
     clear_old: bool,

crates/settings/src/keymap_file.rs

@@ -36,9 +36,6 @@ impl JsonSchema for KeymapAction {
     }
 }
 
-#[derive(Deserialize)]
-struct ActionWithData(Box<str>, Value);
-
 impl KeymapFile {
     pub fn load_asset(asset_path: &str, cx: &mut AppContext) -> Result<()> {
         let content = asset_str::<SettingsAssets>(asset_path);