Expiration does not release hard disk space

[mharlach]

Description

When setting an expiration value there is an expectation that once the key/value has been expired that the entity is removed from the storage collection. When working on systems with limited hard disk space or where hard disk is heavily regulated, this presents an issue because when using the Disk or SQLite provider, the storage file/directory continues to grow.

Short of flushing the entire cache, there is no way to remove the unused cache entries.