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/gpui/examples/input.rs

@@ -3,10 +3,10 @@ use std::ops::Range;
 use gpui::{
     actions, black, div, fill, hsla, opaque_grey, point, prelude::*, px, relative, rgb, rgba, size,
     white, yellow, App, Application, Bounds, ClipboardItem, Context, CursorStyle, ElementId,
-    ElementInputHandler, Entity, FocusHandle, Focusable, GlobalElementId, KeyBinding, Keystroke,
-    LayoutId, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent, PaintQuad, Pixels, Point,
-    ShapedLine, SharedString, Style, TextRun, UTF16Selection, UnderlineStyle, ViewInputHandler,
-    Window, WindowBounds, WindowOptions,
+    ElementInputHandler, Entity, EntityInputHandler, FocusHandle, Focusable, GlobalElementId,
+    KeyBinding, Keystroke, LayoutId, MouseButton, MouseDownEvent, MouseMoveEvent, MouseUpEvent,
+    PaintQuad, Pixels, Point, ShapedLine, SharedString, Style, TextRun, UTF16Selection,
+    UnderlineStyle, Window, WindowBounds, WindowOptions,
 };
 use unicode_segmentation::*;
 
@@ -257,7 +257,7 @@ impl TextInput {
     }
 }
 
-impl ViewInputHandler for TextInput {
+impl EntityInputHandler for TextInput {
     fn text_for_range(
         &mut self,
         range_utf16: Range<usize>,