fix revalidation issue with route handlers (#63213)
### What
When a route handler uses an API that opts it into dynamic rendering
(such as `no-store` on a fetch), and also specifies a `revalidate` time,
the `revalidate` time is ignored and route is treated as fully static.
### Why
`revalidate: 0` and `revalidate: false` have different semantic
meanings: `false` essentially means cache forever, whereas `0` means
it's dynamic. Since `0` is also falsey, the code we have to fallback
with a default `revalidate` value for route handlers is incorrectly not
marking the route as dynamic, and as a result, caching the route without
an expiration time.
### How
This updates the fallback handling for app routes respect a revalidation
value of `0`, so that the page can properly be marked dynamic.
### Test Explanation
This adds 2 new routes handlers: both have a revalidation time specified
& use `no-store` on a fetch, but only one of them specifies `export
const dynamic = 'force-static'`. The one that doesn't specify
`force-static` is correctly omitted from the prerender manifest. The one
that is `force-static` is correctly in the prerender manifest with the
right expiration time. An additional test case was added to verify that
this data refreshes after the specified interval.
Closes NEXT-2764
