[PP] Validate Shell prefetches (except gSP) (#95151)
Implements instant validation for `partialPrefetching`. In this mode,
`<Link>` prefetches an App Shell, which cannot access link data, and we
need to warn for that.
The changes in `instant-validation.tsx` are relatively simple: for an
App Shell, we simply use `ShellRuntime` for all the new segments. We
might also force them into `Runtime` for the purposes of discriminating
dynamic holes. If a hole is present in `ShellRuntime` but disappears in
`Runtime`, then we know it's caused by **link data** (as opposed to
runtime or dynamic data). I've added some new error messages for this
case.
Note that the implementation here is incomplete: it uses the chunks from
the dev render, which resolves static params in the `Static` stage. We
use `ShellRuntime` for validating the App Shell, so as a result, static
params are incorrectly included in it and don't trigger link data
errors. This will be implemented in a follow-up.
Note: It seems like we have some pre-existing bug in build validation
where `fallbackParams` aren't populated, so params resolve statically
when they shouldn't. I've marked two tests with `// TODO(app-shells):
missing fallback params in build validation` so we can follow up and fix
those.
