Initial implementation of anonymous_pipe

Co-authored-by: Alphyr <47725341+a1phyr@users.noreply.github.com>
Co-authored-by: Jubilee <46493976+workingjubilee@users.noreply.github.com>
Signed-off-by: Jiahao XU <Jiahao_XU@outlook.com>

library/std/src/lib.rs

@@ -590,6 +590,8 @@ pub mod panic;
 #[unstable(feature = "core_pattern_types", issue = "none")]
 pub mod pat;
 pub mod path;
+#[unstable(feature = "anonymous_pipe", issue = "127154")]
+pub mod pipe;
 pub mod process;
 pub mod sync;
 pub mod time;