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/storybook/src/stories/indent_guides.rs

@@ -33,7 +33,7 @@ impl IndentGuidesStory {
 }
 
 impl Render for IndentGuidesStory {
-    fn render(&mut self, window: &mut Window, cx: &mut ModelContext<Self>) -> impl IntoElement {
+    fn render(&mut self, window: &mut Window, cx: &mut Context<Self>) -> impl IntoElement {
         Story::container()
             .child(Story::title("Indent guides"))
             .child(