Bug report

Bug description:

We try to load the channel end types from "test.support.interpreters.channel", which doesn't exist.

CPython versions tested on:

CPython main branch

Operating systems tested on:

No response

Linked PRs

• gh-121596: Fix Sharing Interpreter Channels #121597
• [3.13] gh-121596: Fix Sharing Interpreter Channels (gh-121597) #121600