editor: Show code actions in mouse context menu (#28677)

Closes #27989

Asynchronous fetch of code actions on right-click, and shows them in
context menu.


https://github.com/user-attachments/assets/413eb0dd-cd1c-4628-a6f1-84eac813da32

Release Notes:

- Improved visibility of code actions by showing them in right-click
context menu.

crates/editor/src/actions.rs

@@ -99,6 +99,9 @@ pub struct ComposeCompletion {
 pub struct ConfirmCodeAction {
     #[serde(default)]
     pub item_ix: Option<usize>,
+    #[serde(default)]
+    #[serde(skip)]
+    pub from_mouse_context_menu: bool,
 }
 
 #[derive(PartialEq, Clone, Deserialize, Default, JsonSchema)]