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/scrolling.rs

@@ -1,4 +1,7 @@
-use egui::{scroll_area::ScrollBarVisibility, *};
+use egui::{
+    pos2, scroll_area::ScrollBarVisibility, Align, Align2, Color32, DragValue, NumExt, Rect,
+    ScrollArea, Sense, Slider, Style, TextStyle, TextWrapMode, Ui, Vec2, Widget,
+};
 
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
 #[derive(Clone, Copy, Debug, PartialEq)]