Stabilize back-forward-cache test cases (#78735)
This attempts to stabilize the back-forward-cache test assertions by
adding retry to the initial button incrementing as I have a theory this
was attempting to click before the event listeners were attached causing
the clicks to be missed which makes the successive test cases fail.
x-ref:
https://github.com/vercel/next.js/actions/runs/14766354734/job/41458564789#step:33:481
x-ref:
https://github.com/vercel/next.js/actions/runs/14766354734/job/41459734942#step:33:191
