Warn on missing debug implementations

This was removed by accident; only the `feature = "rustc-dep-of-std"`
gate should have been removed.

Fixes: a6e7563 ("Always implement `Debug`")

(backport <#4715>)
(cherry picked from commit 833eb19)

Author: tgross35

src/lib.rs

@@ -9,6 +9,11 @@
     unused_macros,
     unused_macro_rules,
 )]
+#![warn(
+    missing_copy_implementations,
+    missing_debug_implementations,
+    safe_packed_borrows
+)]
 // Prepare for a future upgrade
 #![warn(rust_2024_compatibility)]
 // Things missing for 2024 that are blocked on MSRV or breakage
@@ -25,7 +30,6 @@
 #![cfg_attr(feature = "rustc-dep-of-std", allow(internal_features))]
 // DIFF(1.0): The thread local references that raise this lint were removed in 1.0
 #![cfg_attr(feature = "rustc-dep-of-std", allow(static_mut_refs))]
-#![warn(missing_copy_implementations, safe_packed_borrows)]
 #![cfg_attr(not(feature = "rustc-dep-of-std"), no_std)]
 #![cfg_attr(feature = "rustc-dep-of-std", no_core)]