dillon1000/react

Regression test: Stylesheet suspends indefinitely when part of error boundary UI during initial hydration (#27258)

Adds a failing test for a case discovered by Next.js. An error boundary
is triggered during initial hydration, and the error fallback includes a
stylesheet. If the stylesheet has not yet been loaded, the commit
suspends, but never resolves even after the stylesheet finishes loading.

Triggering this bug depends on several very specific code paths being
triggered simultaneously. There are a few ways we could fix the bug;
I'll submit as one or more separate PRs to show that each one is
sufficient.