Auto merge of rust-lang#84560 - cjgillot:inline-iter, r=m-ou-se

Inline Iterator as IntoIterator.

For some reason, it appears on rustc's own perf stats.

Author: bors

Diff for: core/src/iter/traits/collect.rs

@@ -238,6 +238,7 @@ impl<I: Iterator> IntoIterator for I {
     type Item = I::Item;
     type IntoIter = I;
 
+    #[inline]
     fn into_iter(self) -> I {
         self
     }