Handle redirections

### Test cases

```
tac | rev 1>&2
```

Will not show any output.

---

```
ls nonexist 2>/dev/null
```

can be also written as:

```
2>/dev/null ls notexist
```

This also works:

```
ls 2>file.txt notexist
```

Idea:

No file or test entry point is named. Start by running the listed commands and tracing how the shell parses and executes them; done means the examples with 2> redirect stderr as shown, including redirection before the command and redirection to a file.

Written by the indexing model from the issue text.