Track navigation timestamp on CacheNode (#77251)
Adds a field `navigatedAt` to the CacheNode type. It represents the
timestamp of the navigation that last updated the CacheNode's data.
This will be used to implement the `staleTimes.dynamic` configuration
option, which allows dynamic data to be stale in the UI up to the given
threshold. This first PR adds the field without changing any behavior.
Originally I was going to call this `requestedAt`, but I have
intentionally chosen not to distinguish between whether the data was
fetched from the network or from the prefetch cache. This means that
even fully static data will respect the `staleTimes.dynamic`
configuration option. In practice, this only matters if the dynamic
stale time is longer than the static one, although usually static stale
times will be larger anyway.
