Enable the clippy::pedantic lint group (#8429)

Instead of opting in to pedantic lints one by one, enable the whole
group and opt out of the noisy ones.

64% of the pedantic lints were already listed individually. This deletes
90 explicit lint lines, enables 51 pedantic lints we never listed, and
picks up new pedantic lints for free. Each opt-out carries its hit
count, so the cost of turning one back on is visible.

`restriction` and `nursery` stay opt-in per lint.

Stacked on top of #8430, which fixes the one real bug the new lints
found.

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

---------

Co-authored-by: Claude Opus 5 (1M context) <noreply@anthropic.com>

crates/egui/src/context.rs

@@ -1761,11 +1761,11 @@ impl Context {
                 .get(&id)
                 .map(|v| v.repaint.cumulative_frame_nr)
                 .unwrap_or_else(|| {
-                    if cfg!(debug_assertions) {
-                        panic!("cumulative_frame_nr_for failed to find the viewport {id:?}");
-                    } else {
-                        0
-                    }
+                    debug_assert!(
+                        false,
+                        "cumulative_frame_nr_for failed to find the viewport {id:?}"
+                    );
+                    0
                 })
         })
     }

crates/egui/src/id.rs

@@ -41,6 +41,13 @@ impl<T: core::hash::Hash + core::fmt::Debug> AsId for T {}
 /// This is niche-optimized to that `Option<Id>` is the same size as `Id`.
 #[derive(Clone, Copy, Hash, Eq, PartialEq)]
 #[cfg_attr(feature = "serde", derive(serde::Deserialize, serde::Serialize))]
+#[cfg_attr(
+    feature = "serde",
+    expect(
+        clippy::unsafe_derive_deserialize,
+        reason = "`from_high_entropy_bits` is only `unsafe` about entropy, not memory safety"
+    )
+)]
 pub struct Id(NonZeroU64);
 
 impl nohash_hasher::IsEnabled for Id {}