[Cache Components] Only validate the shell on SSR render (#82381)
Prior to this change on every navigation we would validate that the
initial static shell satisified the rules of cache components. This
offers more protection as you edit pages but it slows down navigations
and we are already concerned with dev speed and the extra CPU contention
can potenially hide or exacerbate other performance characteristics you
might notice in dev.
So for now we will only validate a page on initial load. This means that
if you are trying to debug a page's static shell suitability you will
need to refresh the page not just navigate to and from it.