Remove wildcard imports (#5018)

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I removed (I hope so) all wildcard imports I found.

For me on my pc this improved the build time:
- for egui -5s
- for eframe -12s

* [x] I have followed the instructions in the PR template

crates/egui_demo_lib/src/demo/misc_demo_window.rs

@@ -1,6 +1,9 @@
-use super::*;
+use super::{Demo, View};
 
-use egui::*;
+use egui::{
+    vec2, Align, Checkbox, CollapsingHeader, Color32, Context, FontId, Frame, Resize, RichText,
+    Sense, Slider, Stroke, TextFormat, TextStyle, Ui, Vec2, Window,
+};
 
 /// Showcase some ui code
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]