THRIFT-5306: Rust code and generated code no longer has clippy warnings (Rust 1.40)

Client: rs

NOTE: Also properly update the min/max supported Rust versions
diff --git a/lib/rs/src/transport/mem.rs b/lib/rs/src/transport/mem.rs
index 68fb265..fe1c543 100644
--- a/lib/rs/src/transport/mem.rs
+++ b/lib/rs/src/transport/mem.rs
@@ -153,7 +153,9 @@
             WriteHalf {
                 handle: TBufferChannel {
                     read: self.read.clone(),
-                    write: self.write.clone(),
+                    // NOTE: not cloning here, since this is the last statement
+                    // in this method and `write` can take ownership of `self.write`
+                    write: self.write,
                 },
             },
         ))