Fix missed renames in #22632 (#23688)

Fix a bug where a GPUI macro still used `ModelContext`
Rename `AsyncAppContext` -> `AsyncApp`
Rename update_model, read_model, insert_model, and reserve_model to
update_entity, read_entity, insert_entity, and reserve_entity

Release Notes:

- N/A

crates/language_models/src/provider/copilot_chat.rs

@@ -11,8 +11,8 @@ use futures::future::BoxFuture;
 use futures::stream::BoxStream;
 use futures::{FutureExt, StreamExt};
 use gpui::{
-    percentage, svg, Animation, AnimationExt, AnyView, App, AsyncAppContext, Entity, Render,
-    Subscription, Task, Transformation,
+    percentage, svg, Animation, AnimationExt, AnyView, App, AsyncApp, Entity, Render, Subscription,
+    Task, Transformation,
 };
 use language_model::{
     LanguageModel, LanguageModelCompletionEvent, LanguageModelId, LanguageModelName,
@@ -190,7 +190,7 @@ impl LanguageModel for CopilotChatLanguageModel {
     fn stream_completion(
         &self,
         request: LanguageModelRequest,
-        cx: &AsyncAppContext,
+        cx: &AsyncApp,
     ) -> BoxFuture<'static, Result<BoxStream<'static, Result<LanguageModelCompletionEvent>>>> {
         if let Some(message) = request.messages.last() {
             if message.contents_empty() {
@@ -266,7 +266,7 @@ impl LanguageModel for CopilotChatLanguageModel {
         _name: String,
         _description: String,
         _schema: serde_json::Value,
-        _cx: &AsyncAppContext,
+        _cx: &AsyncApp,
     ) -> BoxFuture<'static, Result<BoxStream<'static, Result<String>>>> {
         future::ready(Err(anyhow!("not implemented"))).boxed()
     }