bpo-46128: Strip IsolatedAsyncioTestCase frames from reported stacktraces (#30196)

* Strip IsolatedAsyncioTestCase frames from reported stacktraces

* Update Misc/NEWS.d/next/Library/2021-12-19-10-47-24.bpo-46128.Qv3EK1.rst

Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>

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Co-authored-by: Kumar Aditya <59607654+kumaraditya303@users.noreply.github.com>
Co-authored-by: Ezio Melotti <ezio.melotti@gmail.com>
Co-authored-by: Hugo van Kemenade <hugovk@users.noreply.github.com>