Ensure client filter with basePath is correct (#60580)
Follow-up to https://github.com/vercel/next.js/pull/60542 this adds
regression tests for `basePath` with the client router filter to ensure
we hard navigate to the correct URL when going from pages -> app.
x-ref: https://github.com/vercel/next.js/issues/47486
Closes NEXT-2086
