Auto merge of #120486 - reitermarkus:use-generic-nonzero, r=dtolnay

Use generic `NonZero` internally.

Tracking issue: https://github.com/rust-lang/rust/issues/120257

library/proc_macro/src/lib.rs

@@ -26,6 +26,7 @@
 #![feature(staged_api)]
 #![feature(allow_internal_unstable)]
 #![feature(decl_macro)]
+#![feature(generic_nonzero)]
 #![feature(maybe_uninit_write_slice)]
 #![feature(negative_impls)]
 #![feature(new_uninit)]