HotEntryCache will update Instants only once per second

Calling Instant.now() several hundred thousand times per
second can be expensive. In my measurements >10% of the
time spend when loading new data was spend calling
Instant.now().
Fixed this by storing an Instant as static member and
updating it periodically in a separate thread.

performanceDb/src/main/java/org/lucares/performance/db/TagsToFile.java

@@ -71,7 +71,7 @@ public class TagsToFile implements AutoCloseable {
 	public TagsToFile(final DataStore dataStore) {
 		this.dataStore = dataStore;
 
-		writerCache = new HotEntryCache<>(Duration.ofSeconds(10));
+		writerCache = new HotEntryCache<>(Duration.ofSeconds(10), "writerCache");
 		writerCache.addListener(new RemovalListener(), EventType.EVICTED, EventType.REMOVED);
 
 	}