Rollup merge of rust-lang#76056 - pickfire:patch-10, r=jyn514

Add more info for Vec Drain doc

See its documentation for more

Author: RalfJung

library/alloc/src/vec.rs

@@ -3037,6 +3037,7 @@ impl<T> AsIntoIter for IntoIter<T> {
 /// A draining iterator for `Vec<T>`.
 ///
 /// This `struct` is created by [`Vec::drain`].
+/// See its documentation for more.
 #[stable(feature = "drain", since = "1.6.0")]
 pub struct Drain<'a, T: 'a> {
     /// Index of tail to preserve