Reuse conversation cache when streaming edits (#30245)

Release Notes:

- Improved latency when the agent applies edits.

crates/assistant_tool/src/assistant_tool.rs

@@ -19,7 +19,7 @@ use gpui::Window;
 use gpui::{App, Entity, SharedString, Task, WeakEntity};
 use icons::IconName;
 use language_model::LanguageModel;
-use language_model::LanguageModelRequestMessage;
+use language_model::LanguageModelRequest;
 use language_model::LanguageModelToolSchemaFormat;
 use project::Project;
 use workspace::Workspace;
@@ -206,7 +206,7 @@ pub trait Tool: 'static + Send + Sync {
     fn run(
         self: Arc<Self>,
         input: serde_json::Value,
-        messages: &[LanguageModelRequestMessage],
+        request: Arc<LanguageModelRequest>,
         project: Entity<Project>,
         action_log: Entity<ActionLog>,
         model: Arc<dyn LanguageModel>,