ARC: Ghost lists aren't queried when getting a value

[erwanor]

Ghost lists for tier-1/tier-2 caches (ARC.t1 and ARC.t2) track "recently" evicted keys.

They are used to react to change in resource usage. In particular, their role is critical in shifting the "cache cursor" ARC.part int left or right (i.e bias balancing toward frequency or recency).

See: https://github.com/aaronwinter/gcache2/blob/master/arc.go#L191