Enable more clippy lints (#6853)

* Follows https://github.com/emilk/egui/pull/6848

crates/egui_demo_app/src/apps/custom3d_glow.rs

@@ -80,7 +80,7 @@ struct RotatingTriangle {
     vertex_array: glow::VertexArray,
 }
 
-#[allow(unsafe_code)] // we need unsafe code to use glow
+#[expect(unsafe_code)] // we need unsafe code to use glow
 impl RotatingTriangle {
     fn new(gl: &glow::Context) -> Option<Self> {
         use glow::HasContext as _;

crates/egui_demo_app/src/apps/custom3d_wgpu.rs

@@ -1,7 +1,7 @@
 use std::num::NonZeroU64;
 
 use eframe::{
-    egui_wgpu::wgpu::util::DeviceExt,
+    egui_wgpu::wgpu::util::DeviceExt as _,
     egui_wgpu::{self, wgpu},
 };
 

crates/egui_demo_app/src/backend_panel.rs

@@ -110,7 +110,7 @@ impl BackendPanel {
         if cfg!(debug_assertions) && cfg!(target_arch = "wasm32") {
             ui.separator();
             // For testing panic handling on web:
-            #[allow(clippy::manual_assert)]
+            #[expect(clippy::manual_assert)]
             if ui.button("panic!()").clicked() {
                 panic!("intentional panic!");
             }

crates/egui_demo_app/src/lib.rs

@@ -10,7 +10,7 @@ pub use wrap_app::{Anchor, WrapApp};
 
 /// Time of day as seconds since midnight. Used for clock in demo app.
 pub(crate) fn seconds_since_midnight() -> f64 {
-    use chrono::Timelike;
+    use chrono::Timelike as _;
     let time = chrono::Local::now().time();
     time.num_seconds_from_midnight() as f64 + 1e-9 * (time.nanosecond() as f64)
 }

crates/egui_demo_app/src/main.rs

@@ -75,7 +75,7 @@ fn start_puffin_server() {
 
             // We can store the server if we want, but in this case we just want
             // it to keep running. Dropping it closes the server, so let's not drop it!
-            #[allow(clippy::mem_forget)]
+            #[expect(clippy::mem_forget)]
             std::mem::forget(puffin_server);
         }
         Err(err) => {

crates/egui_demo_app/src/web.rs

@@ -14,7 +14,7 @@ pub struct WebHandle {
 #[wasm_bindgen]
 impl WebHandle {
     /// Installs a panic hook, then returns.
-    #[allow(clippy::new_without_default)]
+    #[allow(clippy::new_without_default, clippy::allow_attributes)]
     #[wasm_bindgen(constructor)]
     pub fn new() -> Self {
         // Redirect [`log`] message to `console.log` and friends:

crates/egui_demo_app/src/wrap_app.rs

@@ -188,7 +188,7 @@ impl WrapApp {
         // This gives us image support:
         egui_extras::install_image_loaders(&cc.egui_ctx);
 
-        #[allow(unused_mut)]
+        #[allow(unused_mut, clippy::allow_attributes)]
         let mut slf = Self {
             state: State::default(),