CacheboxProvider metadata and stores: use CFML functions on java hash maps breaks concurrency

For example, in Lucee at least, StructKeyArray( pool ) is not thread safe and leads to ArrayIndexOutOfBounds errors while the pool is having entries cleared. Can and should use methods defined on ConcurrentHashMap instead to preserve thread safety of these objects and, indeed, improve performance (my own simple tests showed native methods ~ 3x faster than StructKeyArray())