Initial QSfera import

Server/vendor/github.com/jellydator/ttlcache/v2/metrics.go

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+package ttlcache
+
+// Metrics contains common cache metrics so you can calculate hit and miss rates
+type Metrics struct {
+	// succesful inserts
+	Inserted int64
+	// retrieval attempts
+	Retrievals int64
+	// all get calls that were in the cache (excludes loader invocations)
+	Hits int64
+	// entries not in cache (includes loader invocations)
+	Misses int64
+	// items removed from the cache in any way
+	Evicted int64
+}