Allow nested `EUDOnStart`

```py
def foo():
    EUDOnStart(lambda: EUDOnStart(lambda: None))

EUDOnStart(foo)

# eudplib.utils.eperror.EPError: Can't use EUDOnStart here. See https://cafe.naver.com/edac/69262
```

eudplib currently only supports up to double nested `EUDOnStart` calls: https://github.com/armoha/eudplib/blob/f10e069e0008afa3d473b673c4078b6d8765d105/src/eudplib/maprw/injector/mainloop.py#L85