Allow task context providers to access project env (#17964)

Closes #13106

Release Notes:

- Task context providers now have access to the local shell environment,
allowing local rust tool installations to work

Before:
<img width="1136" alt="Screenshot 2024-09-17 at 22 09 38"
src="https://github.com/user-attachments/assets/7d6c5606-4820-4f6f-92d1-c3d314b9ab42">

After:
<img width="1136" alt="Screenshot 2024-09-17 at 22 09 58"
src="https://github.com/user-attachments/assets/a962e607-15f5-44ce-b53e-a0dbe135f2d8">

crates/language/src/task_context.rs

@@ -25,6 +25,7 @@ pub trait ContextProvider: Send + Sync {
         &self,
         _variables: &TaskVariables,
         _location: &Location,
+        _project_env: Option<&HashMap<String, String>>,
         _cx: &mut AppContext,
     ) -> Result<TaskVariables> {
         Ok(TaskVariables::default())