Allow to toggle git hunk diffs (#11080)

Part of https://github.com/zed-industries/zed/issues/4523

Added two new actions with the default keybindings

```
"cmd-'": "editor::ToggleHunkDiff",
"cmd-\"": "editor::ExpandAllHunkDiffs",
```

that allow to browse git hunk diffs in Zed:


https://github.com/zed-industries/zed/assets/2690773/9a8a7d10-ed06-4960-b4ee-fe28fc5c4768


The hunks are dynamic and alter on user folds and modifications, or
toggle hidden, if the modifications were not adjacent to the expanded
hunk.


Release Notes:

- Added `editor::ToggleHunkDiff` (`cmd-'`) and
`editor::ExpandAllHunkDiffs` (`cmd-"`) actions to browse git hunk diffs
in Zed

crates/outline/Cargo.toml

@@ -13,6 +13,7 @@ path = "src/outline.rs"
 doctest = false
 
 [dependencies]
+collections.workspace = true
 editor.workspace = true
 fuzzy.workspace = true
 gpui.workspace = true

crates/outline/src/outline.rs

@@ -98,6 +98,8 @@ struct OutlineViewDelegate {
     last_query: String,
 }
 
+enum OutlineRowHighlights {}
+
 impl OutlineViewDelegate {
     fn new(
         outline_view: WeakView<OutlineView>,
@@ -150,8 +152,6 @@ impl OutlineViewDelegate {
     }
 }
 
-enum OutlineRowHighlights {}
-
 impl PickerDelegate for OutlineViewDelegate {
     type ListItem = ListItem;
 
@@ -316,6 +316,7 @@ impl PickerDelegate for OutlineViewDelegate {
 
 #[cfg(test)]
 mod tests {
+    use collections::HashSet;
     use gpui::{TestAppContext, VisualTestContext};
     use indoc::indoc;
     use language::{Language, LanguageConfig, LanguageMatcher};
@@ -482,7 +483,10 @@ mod tests {
 
     fn highlighted_display_rows(editor: &View<Editor>, cx: &mut VisualTestContext) -> Vec<u32> {
         editor.update(cx, |editor, cx| {
-            editor.highlighted_display_rows(cx).into_keys().collect()
+            editor
+                .highlighted_display_rows(HashSet::default(), cx)
+                .into_keys()
+                .collect()
         })
     }