Add test to verify that inner caches are excluded from Resume Data Cache (#75883)
The Resume Data Cache (RDC) is used to provide cache consistency when
resuming a partial prerendered static shell. When reading from this
cache, it is not possible for there to be a miss because, regardless of
the cache age, we always consume the cache entries on resume because
they are temporarily bound to the static shell being served for this
particular request. Since the cache entry can never miss, there is no
need to store inner cache entries in the Resume Data Cache because the
only time you would encounter an inner entry is if the outer entry had
to revalidate.
We have already optimized the Resume Data Cache by excluding writing to
it during prerendering (and dev warmup rendering) if we're already
inside a cache scope. We also handle that you can have an inner cache
entry fill the backing cache and omit the RDC entry, and then later we
encounter that same cache entry in the prerender scope, and even though
we don't need to produce a new cache entry (it was already cached in the
backing cache implementation), we do still write it to the Resume Data
Cache.
The test added in this PR verifies this behavior and ensures that we
don't regress in the future.
closes NAR-54