Add test for Version::to_string

src/version.rs

@@ -262,4 +262,14 @@ mod tests {
             }
         )
     }
+
+    #[test]
+    fn to_string() {
+        let s = "3.14.0_beta2-riscv64";
+        let version: Version = s.parse().unwrap();
+        assert_eq!(s, version.to_string());
+        let s = "3.14.6_git_r2d2xxx.1705881493-x86_64";
+        let version: Version = s.parse().unwrap();
+        assert_eq!(s, version.to_string());
+    }
 }