Clean up and unify exercises

exercises/06_move_semantics/move_semantics1.rs

@@ -1,17 +1,3 @@
-// move_semantics1.rs
-//
-// Execute `rustlings hint move_semantics1` or use the `hint` watch subcommand
-// for a hint.
-
-#[test]
-fn main() {
-    let vec0 = vec![22, 44, 66];
-
-    let vec1 = fill_vec(vec0);
-
-    assert_eq!(vec1, vec![22, 44, 66, 88]);
-}
-
 fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
     let vec = vec;
 
@@ -19,3 +5,21 @@ fn fill_vec(vec: Vec<i32>) -> Vec<i32> {
 
     vec
 }
+
+fn main() {
+    // You can optionally experiment here.
+}
+
+#[cfg(test)]
+mod tests {
+    use super::*;
+
+    #[test]
+    fn move_semantics1() {
+        let vec0 = vec![22, 44, 66];
+
+        let vec1 = fill_vec(vec0);
+
+        assert_eq!(vec1, vec![22, 44, 66, 88]);
+    }
+}