Tiered storage removal of local objects should use internal thread

The tiered storage internal thread code supports work operations that drop the local or the shared object and would add those work units to the work queue.

donald.anderson in WT-7514 the code somewhere removes the local file and moves/copies it to a cached area. This ticket should move that code into the work unit processing and let the internal thread do that work. Where is the code that does the reomval from the local directory?