[3.11] GH-95736: fix IsolatedAsyncioTestCase to initialize Runner before calling setup functions (GH-95898)

[miss-islington]

(cherry picked from commit 9d515997f943b7b510268448f372dabcbf957858)

Co-authored-by: Kumar Aditya [email protected]

• Issue: gh-95736

[miss-islington]

Status check is done, and it's a success ✅ .

[miss-islington]

Status check is done, and it's a success ✅ .

[miss-islington]

Status check is done, and it's a success ✅ .

[gvanrossum]

@pablogsal This is the last one I sponsor, I promise.

[miss-islington]

Status check is done, and it's a success ✅ .

[tiran]

The changeset breaks tests on Emscripten.

[kumaraditya303]

Superseded by https://github.com/python/cpython/pull/96042