Previous getFromView would call view.Result when the result may not have been returned
(because the index is updated past the minIndex. This would allocate a slice and sort it
for no reason, because the values would never be returned.
Fix this by re-ordering the operations in getFromView.
The test changes in this commit were an attempt to cover the case where
an update is received but the index does not exceed the minIndex.
Also rename it to readEntry now that it doesn't return the entire entry. Based on feedback
in PR review, the full entry is not used by the caller, and accessing the fields wouldn't be
safe outside the lock, so it is safer to return only the Materializer
The idleTTL was being written and read concurrently. Instead move the idleTTL to a struct
field so that when one test patches the TTL it does not impact others.
The background goroutines for the store can outlive a test because context cancellation
is async.
Remove View.Result error return value, it was always nil, and seems like it will likely always remain nill
since it is simply reading a stored value.
Also replace some cache types with local types.
And only start expiration time when the last request ends. This makes tracking expiry simpler, and
ensures that no entry can be expired while there are active requests.
