test: allow-runtime breaks Link's Server component child detection (#95596)
See NAR-876. We discovered this problem in #95384, when removing the
Early/Late stage split, but it turns out that this was a preexisting
race that occurs for runtime-prefetchable segments the problem existed
before for runtime (which currently render in EarlyStatic, a task
earlier than non-runtime-prefetchable segments)
adds failing tests for `passHref` with allow-runtime (i.e. when the
segment runs early), and passing tests for it in the dynamic stage (when
the passHref is gated behind dynamic, which seems to delay it long
enough for the debug channel to initialize)