Reformat rust code using 1.40 rustfmt and fail build if rustfmt fails (#2339)

diff --git a/lib/rs/src/transport/mod.rs b/lib/rs/src/transport/mod.rs
index d02a87c..2b5733f 100644
--- a/lib/rs/src/transport/mod.rs
+++ b/lib/rs/src/transport/mod.rs
@@ -111,7 +111,12 @@
     /// Returned halves may share the underlying OS channel or buffer resources.
     /// Implementations **should ensure** that these two halves can be safely
     /// used independently by concurrent threads.
-    fn split(self) -> crate::Result<(crate::transport::ReadHalf<Self>, crate::transport::WriteHalf<Self>)>
+    fn split(
+        self,
+    ) -> crate::Result<(
+        crate::transport::ReadHalf<Self>,
+        crate::transport::WriteHalf<Self>,
+    )>
     where
         Self: Sized;
 }