Incorrect nested error wrapped to ArrowError:External variant for joins

[DDtKey]

Describe the bug
This line of code makes impossible to get real reason of error.

.map_err(|e| ArrowError::ExternalError(e.to_string().into())),

It could produce such error: External error: Arrow error: External error: Arrow error: External error: Arrow error: External error: Arrow error: Csv error: ... as a string-message, not a type

That's actually really bad, because under Csv error it could be useful info. But instead of this I receive text error with too many nested External variants.

To Reproduce
Occurrence depends on execution plan and my data that caused this is rather large.
I believe it should be possible to cover with simple test of error type:

    #[tokio::test]
    async fn check_error_nesting() {
        let once_fut = OnceFut::<()>::new(async {
            Err(DataFusionError::ArrowError(ArrowError::CsvError("some error".to_string())))
        });

        struct TestFut(OnceFut<()>);
        impl Future for TestFut {
            type Output = ArrowResult<()>;

            fn poll(mut self: Pin<&mut Self>, cx: &mut Context<'_>) -> Poll<Self::Output> {
                match ready!((&mut self.0).get(cx)) {
                    Ok(()) => Poll::Ready(Ok(())),
                    Err(e) => Poll::Ready(Err(e)),
                }
            }
        }

        let res = TestFut(once_fut).await;
        let err = res.expect_err("future always return err");
        // ... some checks of error type

    }

Expected behavior
I expect to be able to take error type instead of message in string format.
However, I see that it's reference and need to figure out right way to handle this case. But current one breaks error handling system for datafustion.

Additional context
I would like to fix this behavior

And it probably make sense to request implementing find_root for arrow (like exists for datafusion error) - but that's out of scope

[alamb]

Possibly related #4991 and apache/arrow-rs#3567

[DDtKey]

@alamb don't think so, check #4983, I made a fix. It had to_string() usage, so it was impossible to downcast error to relevant error type