[Instant] Fix crash with search params (#89922)
In dev validation, we're disassembling a payload from a dynamic render.
If the request had search params, page segments in the router state will
have them attached: `__PAGE__?{"q":"123"}`. In
`findNavigationsToValidate`, we do the equivalent of constructing a
flightRouterState, so we need to match that, otherwise we'll name the
segment `__PAGE__` instead and then can't look it up in the cache, and
crash during validation.
