eframe: Replace Frame::update with fn logic and fn ui (#7775)

* Part of https://github.com/emilk/egui/issues/5113
* Part of https://github.com/emilk/egui/issues/3524

## What
This deprecates `eframe::App::update` and replaces it with two new
functions:

```rs
pub trait App {
	/// Called just before `ui`, and in the future this will
    /// also be called for background apps when needed.
	fn logic(&mut self, ctx: &egui::Context, frame: &mut Frame) { }
	
    /// Show your user interface to the user.
	fn ui(&mut self, ui: &mut egui::Ui, frame: &mut Frame);

	…
}
```

Similarly, `Context::run` is deprecated in favor of `Context::run_ui`.

`Plugin`s are now handed a `Ui` instead of just a `Context` in
`on_begin/end_frame`.

## TODO
…either in this PR or a later one
* [x] Deprecate `App::update`
* [x] Deprecate `Context::run`
* [x] Change plugins to get a `Ui`
* [x] Update kittest
* [x] Change viewports to get UI:s (`show_viewport_immediate` etc)
  - https://github.com/emilk/egui/pull/7779

## Later PRs
* [ ] Deprecate `Panel::show`
* [ ] Deprecate `CentralPanel::show`
* [ ] Deprecate `CentralPanel` ?

crates/egui_demo_lib/src/demo/demo_app_windows.rs

@@ -372,7 +372,7 @@ fn file_menu_button(ui: &mut Ui) {
 mod tests {
     use crate::{Demo as _, demo::demo_app_windows::DemoGroups};
 
-    use egui_kittest::kittest::{NodeT as _, Queryable as _};
+    use egui_kittest::kittest::Queryable as _;
     use egui_kittest::{Harness, OsThreshold, SnapshotOptions, SnapshotResults};
 
     #[test]
@@ -394,12 +394,15 @@ mod tests {
 
             let name = remove_leading_emoji(demo.name());
 
-            let mut harness = Harness::new(|ctx| {
-                egui_extras::install_image_loaders(ctx);
-                demo.show(ctx, &mut true);
+            let mut harness = Harness::new_ui(|ui| {
+                egui_extras::install_image_loaders(ui);
+                demo.show(ui, &mut true);
             });
 
-            let window = harness.queryable_node().children().next().unwrap();
+            let window = harness
+                .get_all_by_role(egui::accesskit::Role::Window)
+                .next()
+                .unwrap();
             // TODO(lucasmerlin): Windows should probably have a label?
             //let window = harness.get_by_label(name);
 

crates/egui_demo_lib/src/demo/modals.rs

@@ -176,9 +176,9 @@ mod tests {
             ..Modals::default()
         };
 
-        let mut harness = Harness::new_state(
-            |ctx, modals| {
-                modals.show(ctx, &mut true);
+        let mut harness = Harness::new_ui_state(
+            |ui, modals| {
+                modals.show(ui, &mut true);
             },
             initial_state,
         );
@@ -204,9 +204,9 @@ mod tests {
             ..Modals::default()
         };
 
-        let mut harness = Harness::new_state(
-            |ctx, modals| {
-                modals.show(ctx, &mut true);
+        let mut harness = Harness::new_ui_state(
+            |ui, modals| {
+                modals.show(ui, &mut true);
             },
             initial_state,
         );
@@ -228,9 +228,9 @@ mod tests {
             ..Modals::default()
         };
 
-        let mut harness = Harness::new_state(
-            |ctx, modals| {
-                modals.show(ctx, &mut true);
+        let mut harness = Harness::new_ui_state(
+            |ui, modals| {
+                modals.show(ui, &mut true);
             },
             initial_state,
         );
@@ -258,9 +258,9 @@ mod tests {
             ..Modals::default()
         };
 
-        let mut harness = Harness::new_state(
-            |ctx, modals| {
-                modals.show(ctx, &mut true);
+        let mut harness = Harness::new_ui_state(
+            |ui, modals| {
+                modals.show(ui, &mut true);
             },
             initial_state,
         );

crates/egui_demo_lib/src/demo/text_edit.rs

@@ -120,9 +120,9 @@ mod tests {
     #[test]
     pub fn should_type() {
         let text = "Hello, world!".to_owned();
-        let mut harness = Harness::new_state(
-            move |ctx, text| {
-                CentralPanel::default().show(ctx, |ui| {
+        let mut harness = Harness::new_ui_state(
+            move |ui, text| {
+                CentralPanel::default().show_inside(ui, |ui| {
                     ui.text_edit_singleline(text);
                 });
             },