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_glow/src/winit.rs

@@ -65,7 +65,7 @@ impl EguiGlow {
     }
 
     /// Call [`Self::paint`] later to paint.
-    pub fn run(&mut self, window: &winit::window::Window, run_ui: impl FnMut(&egui::Context)) {
+    pub fn run(&mut self, window: &winit::window::Window, run_ui: impl FnMut(&mut egui::Ui)) {
         let raw_input = self.egui_winit.take_egui_input(window);
 
         let egui::FullOutput {
@@ -74,7 +74,7 @@ impl EguiGlow {
             shapes,
             pixels_per_point,
             viewport_output,
-        } = self.egui_ctx.run(raw_input, run_ui);
+        } = self.egui_ctx.run_ui(raw_input, run_ui);
 
         if viewport_output.len() > 1 {
             log::warn!("Multiple viewports not yet supported by EguiGlow");