Rollup merge of rust-lang#86121 - nickshiling:forwarding_impl_for_seek_trait_stream_position, r=dtolnay

Forwarding implementation for Seek trait's stream_position method

Forwarding implementations for `Seek` trait's `stream_position` were missed when it was stabilized in `1.51.0`

Author: JohnTitor

library/std/src/io/impls.rs

@@ -87,6 +87,11 @@ impl<S: Seek + ?Sized> Seek for &mut S {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (**self).seek(pos)
     }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for &mut B {
@@ -186,6 +191,11 @@ impl<S: Seek + ?Sized> Seek for Box<S> {
     fn seek(&mut self, pos: SeekFrom) -> io::Result<u64> {
         (**self).seek(pos)
     }
+
+    #[inline]
+    fn stream_position(&mut self) -> io::Result<u64> {
+        (**self).stream_position()
+    }
 }
 #[stable(feature = "rust1", since = "1.0.0")]
 impl<B: BufRead + ?Sized> BufRead for Box<B> {