FileInfoCache.Get previously acquired TWO locks on every cache hit:
1. RLock → check existence + TTL
2. Release RLock → Lock → MoveToFront (LRU update) → Unlock
The MoveToFront on every hit forced a read-to-write lock upgrade,
creating contention under concurrent reads.
Apply approximate LRU: skip MoveToFront on Get (read) path entirely.
LRU position is only updated in Set (write) path. This is the same
pattern already used by internal/cache/file_cache.go.
Result: Get fast path reduced from 2 lock acquisitions to 1 RLock.
TTL-expired entries still use double-check locking for safe removal.
xfy
e44cfc7128