fix: Prevent infinite recursion of bounds formatting

[ShoyuVanilla]

Fixes #19007

I've inserted extra tracings in scip and found out the exact position causing the issue:

https://docs.rs/futures-util/latest/src/futures_util/stream/try_stream/try_concat.rs.html#40

impl<St> Future for TryConcat<St>
where
    St: TryStream,
    St::Ok: Extend<<St::Ok as IntoIterator>::Item> + IntoIterator + Default,
{
    type Output = Result<St::Ok, St::Error>;

    fn poll(self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
        let mut this = self.project();

        Poll::Ready(Ok(loop {
            if let Some(x) = ready!(this.stream.as_mut().try_poll_next(cx)?) {
                      //^ This token
                if let Some(a) = this.accum {
                    a.extend(x)
                } else {
                    *this.accum = Some(x)
                }
            } else {
                break this.accum.take().unwrap_or_default();
            }
        }))
    }
}

the x on the above code has the type St::Ok and the bounds St::Ok: Extend<<**St::Ok** as IntoIterator>::Item> + IntoIterator + Default and this is causing the infinite recursion, as @glandium said

[Veykril]

Can we make this an inlay hint test and put it beside the tests introduced by #18925 so we've got them in the same area?

[Veykril]

I feel like we might wanna move this down into the if !bounds.is_empty() { branch body? Recursive bounds like these will be the minority and so we prevent triggering a heap alloc in the case where we aren't actually doing the different rendering here (but only realize so within this closure.