Make WidgetText smaller and faster (#6903)

* In preparation of #5830, this should reduce the performance impact of
that PR

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Co-authored-by: Emil Ernerfeldt <emil.ernerfeldt@gmail.com>

crates/egui_demo_app/src/wrap_app.rs

@@ -134,7 +134,7 @@ impl std::fmt::Display for Anchor {
 
 impl From<Anchor> for egui::WidgetText {
     fn from(value: Anchor) -> Self {
-        Self::RichText(egui::RichText::new(value.to_string()))
+        Self::from(value.to_string())
     }
 }