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

diff --git a/lib/rs/src/server/mod.rs b/lib/rs/src/server/mod.rs
index 050feee..64c6da2 100644
--- a/lib/rs/src/server/mod.rs
+++ b/lib/rs/src/server/mod.rs
@@ -91,7 +91,8 @@
     /// the response to `o`.
     ///
     /// Returns `()` if the handler was executed; `Err` otherwise.
-    fn process(&self, i: &mut dyn TInputProtocol, o: &mut dyn TOutputProtocol) -> crate::Result<()>;
+    fn process(&self, i: &mut dyn TInputProtocol, o: &mut dyn TOutputProtocol)
+        -> crate::Result<()>;
 }
 
 /// Convenience function used in generated `TProcessor` implementations to