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/ui/src/components/icon.rs

@@ -49,7 +49,7 @@ impl From<AnimationElement<Icon>> for AnyIcon {
 }
 
 impl RenderOnce for AnyIcon {
-    fn render(self, _cx: &mut WindowContext) -> impl IntoElement {
+    fn render(self, _window: &mut Window, _cx: &mut App) -> impl IntoElement {
         match self {
             Self::Icon(icon) => icon.into_any_element(),
             Self::AnimatedIcon(animated_icon) => animated_icon.into_any_element(),
@@ -88,8 +88,8 @@ impl IconSize {
     /// The returned tuple contains:
     ///   1. The length of one side of the square
     ///   2. The padding of one side of the square
-    pub fn square_components(&self, cx: &mut WindowContext) -> (Pixels, Pixels) {
-        let icon_size = self.rems() * cx.rem_size();
+    pub fn square_components(&self, window: &mut Window, cx: &mut App) -> (Pixels, Pixels) {
+        let icon_size = self.rems() * window.rem_size();
         let padding = match self {
             IconSize::Indicator => DynamicSpacing::Base00.px(cx),
             IconSize::XSmall => DynamicSpacing::Base02.px(cx),
@@ -102,8 +102,8 @@ impl IconSize {
     }
 
     /// Returns the length of a side of the square that contains this [`IconSize`], with padding.
-    pub fn square(&self, cx: &mut WindowContext) -> Pixels {
-        let (icon_size, padding) = self.square_components(cx);
+    pub fn square(&self, window: &mut Window, cx: &mut App) -> Pixels {
+        let (icon_size, padding) = self.square_components(window, cx);
 
         icon_size + padding * 2.
     }
@@ -408,7 +408,7 @@ impl Icon {
 }
 
 impl RenderOnce for Icon {
-    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
+    fn render(self, _: &mut Window, cx: &mut App) -> impl IntoElement {
         match self.source {
             IconSource::Svg(path) => svg()
                 .with_transformation(self.transformation)
@@ -461,7 +461,7 @@ impl IconWithIndicator {
 }
 
 impl RenderOnce for IconWithIndicator {
-    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
+    fn render(self, _window: &mut Window, cx: &mut App) -> impl IntoElement {
         let indicator_border_color = self
             .indicator_border_color
             .unwrap_or_else(|| cx.theme().colors().elevated_surface_background);
@@ -486,7 +486,7 @@ impl RenderOnce for IconWithIndicator {
 }
 
 impl ComponentPreview for Icon {
-    fn examples(_cx: &mut WindowContext) -> Vec<ComponentExampleGroup<Icon>> {
+    fn examples(_window: &mut Window, _cx: &mut App) -> Vec<ComponentExampleGroup<Icon>> {
         let arrow_icons = vec![
             IconName::ArrowDown,
             IconName::ArrowLeft,