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/divider.rs

@@ -24,7 +24,7 @@ pub enum DividerColor {
 }
 
 impl DividerColor {
-    pub fn hsla(self, cx: &WindowContext) -> Hsla {
+    pub fn hsla(self, cx: &mut App) -> Hsla {
         match self {
             DividerColor::Border => cx.theme().colors().border,
             DividerColor::BorderVariant => cx.theme().colors().border_variant,
@@ -41,7 +41,7 @@ pub struct Divider {
 }
 
 impl RenderOnce for Divider {
-    fn render(self, cx: &mut WindowContext) -> impl IntoElement {
+    fn render(self, _: &mut Window, cx: &mut App) -> impl IntoElement {
         match self.style {
             DividerStyle::Solid => self.render_solid(cx).into_any_element(),
             DividerStyle::Dashed => self.render_dashed(cx).into_any_element(),
@@ -96,7 +96,7 @@ impl Divider {
         self
     }
 
-    pub fn render_solid(self, cx: &WindowContext) -> impl IntoElement {
+    pub fn render_solid(self, cx: &mut App) -> impl IntoElement {
         div()
             .map(|this| match self.direction {
                 DividerDirection::Horizontal => {
@@ -111,7 +111,7 @@ impl Divider {
 
     // TODO: Use canvas or a shader here
     // This obviously is a short term approach
-    pub fn render_dashed(self, cx: &WindowContext) -> impl IntoElement {
+    pub fn render_dashed(self, cx: &mut App) -> impl IntoElement {
         let segment_count = 128;
         let segment_count_f = segment_count as f32;
         let segment_min_w = 6.;