Remove un-necessary socket requirements in pdb async tests

[graingert]

Proposal:

the pdb async tests should run coroutines using coro.send(None) because they don't need an async framework to run. This would remove asyncio from the tests and support running on emscripten/wasi

Has this already been discussed elsewhere?

No response given

Links to previous discussion of this feature:

No response

Linked PRs

• gh-128265: support wasi/emscripten on pdb tests, by removing asyncio from pdb tests #128264