Write access time asynchronously, read synchronouslyFile access times are now written asynchronously while the cache isbeing used. When it's about to be closed, they are now readsynchronously from the cleanup action because the cache access workerhas then already been stopped.
Track artifact cache file access in PersistentIndexedCacheThis commit introduces the `FileAccessJournal` interface and providestwo implementations: ModificationTimeFileAccessJournal:: Reads and sets `File.lastModified()`. IndexedCacheBackedFileAccessJournal:: Uses a PersistentIndexedCache to store the access timestamp.The latter is now used in DefaultCacheLockingManager for the artifactcache. All other PersistentCaches still use the former.