As originally conceived, the local_store extension (and every storage source) would return a file system that managed not only remote (immutable) files but also the current local file.  Our vision evolved, and now storage sources return readonly file systems - specific administration tasks like moving files in and out of shared storage happens on the WT_STORAGE_SOURCE interface, not the WT_FILE_SYSTEM that is returned by it.

The upshot is that there is a bunch of stale and potentially confusing code in local_store.c that can be removed and cleaned up.

This is a "quick-win" ticket for tiered storage.