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/editor/src/test/editor_lsp_test_context.rs

@@ -329,7 +329,7 @@ impl EditorLspTestContext {
     where
         T: 'static + request::Request,
         T::Params: 'static + Send,
-        F: 'static + Send + FnMut(lsp::Url, T::Params, gpui::AsyncAppContext) -> Fut,
+        F: 'static + Send + FnMut(lsp::Url, T::Params, gpui::AsyncApp) -> Fut,
         Fut: 'static + Send + Future<Output = Result<T::Result>>,
     {
         let url = self.buffer_lsp_url.clone();