Eliminate GPUI View, ViewContext, and WindowContext types (#22632)

There's still a bit more work to do on this, but this PR is compiling
(with warnings) after eliminating the key types. When the tasks below
are complete, this will be the new narrative for GPUI:

- `Entity<T>` - This replaces `View<T>`/`Model<T>`. It represents a unit
of state, and if `T` implements `Render`, then `Entity<T>` implements
`Element`.
- `&mut App` This replaces `AppContext` and represents the app.
- `&mut Context<T>` This replaces `ModelContext` and derefs to `App`. It
is provided by the framework when updating an entity.
- `&mut Window` Broken out of `&mut WindowContext` which no longer
exists. Every method that once took `&mut WindowContext` now takes `&mut
Window, &mut App` and every method that took `&mut ViewContext<T>` now
takes `&mut Window, &mut Context<T>`

Not pictured here are the two other failed attempts. It's been quite a
month!

Tasks:

- [x] Remove `View`, `ViewContext`, `WindowContext` and thread through
`Window`
- [x] [@cole-miller @mikayla-maki] Redraw window when entities change
- [x] [@cole-miller @mikayla-maki] Get examples and Zed running
- [x] [@cole-miller @mikayla-maki] Fix Zed rendering
- [x] [@mikayla-maki] Fix todo! macros and comments
- [x] Fix a bug where the editor would not be redrawn because of view
caching
- [x] remove publicness window.notify() and replace with
`AppContext::notify`
- [x] remove `observe_new_window_models`, replace with
`observe_new_models` with an optional window
- [x] Fix a bug where the project panel would not be redrawn because of
the wrong refresh() call being used
- [x] Fix the tests
- [x] Fix warnings by eliminating `Window` params or using `_`
- [x] Fix conflicts
- [x] Simplify generic code where possible
- [x] Rename types
- [ ] Update docs

### issues post merge

- [x] Issues switching between normal and insert mode
- [x] Assistant re-rendering failure
- [x] Vim test failures
- [x] Mac build issue



Release Notes:

- N/A

---------

Co-authored-by: Antonio Scandurra <me@as-cii.com>
Co-authored-by: Cole Miller <cole@zed.dev>
Co-authored-by: Mikayla <mikayla@zed.dev>
Co-authored-by: Joseph <joseph@zed.dev>
Co-authored-by: max <max@zed.dev>
Co-authored-by: Michael Sloan <michael@zed.dev>
Co-authored-by: Mikayla Maki <mikaylamaki@Mikaylas-MacBook-Pro.local>
Co-authored-by: Mikayla <mikayla.c.maki@gmail.com>
Co-authored-by: joão <joao@zed.dev>

crates/evals/src/eval.rs

@@ -6,7 +6,7 @@ use clock::RealSystemClock;
 use collections::BTreeMap;
 use feature_flags::FeatureFlagAppExt as _;
 use git::GitHostingProviderRegistry;
-use gpui::{AsyncAppContext, BackgroundExecutor, Context, Model};
+use gpui::{AppContext as _, AsyncAppContext, BackgroundExecutor, Entity};
 use http_client::{HttpClient, Method};
 use language::LanguageRegistry;
 use node_runtime::NodeRuntime;
@@ -99,7 +99,7 @@ fn main() -> Result<()> {
     let cli = Cli::parse();
     env_logger::init();
 
-    gpui::App::headless().run(move |cx| {
+    gpui::Application::headless().run(move |cx| {
         let executor = cx.background_executor().clone();
         let client = Arc::new(ReqwestClient::user_agent("Zed LLM evals").unwrap());
         cx.set_http_client(client.clone());
@@ -290,9 +290,7 @@ async fn run_evaluation(
             )
         })
         .unwrap();
-    let user_store = cx
-        .new_model(|cx| UserStore::new(client.clone(), cx))
-        .unwrap();
+    let user_store = cx.new(|cx| UserStore::new(client.clone(), cx)).unwrap();
     let node_runtime = NodeRuntime::unavailable();
 
     let evaluations = fs::read(&evaluations_path).expect("failed to read evaluations.json");
@@ -404,11 +402,11 @@ async fn run_evaluation(
 #[allow(clippy::too_many_arguments)]
 async fn run_eval_project(
     evaluation_project: EvaluationProject,
-    user_store: &Model<UserStore>,
+    user_store: &Entity<UserStore>,
     repo_db_path: PathBuf,
     repo_dir: &Path,
     counts: &mut Counts,
-    project: Model<Project>,
+    project: Entity<Project>,
     embedding_provider: Arc<dyn EmbeddingProvider>,
     fs: Arc<dyn Fs>,
     cx: &mut AsyncAppContext,
@@ -547,7 +545,7 @@ async fn run_eval_project(
 }
 
 async fn wait_for_indexing_complete(
-    project_index: &Model<ProjectIndex>,
+    project_index: &Entity<ProjectIndex>,
     cx: &mut AsyncAppContext,
     timeout: Option<Duration>,
 ) {