StorageServer processes likely to see OutOfMemory error after storage engine change

Due to the way different storage engines allocate memory, there is a high risk of running out of memory shortly after one storage engine is closed and another is opened.

The Memory, SQLite, and Redwood storage engines all use different `FastAllocator` sizes for the bulk of their memory usage, so when switching from any of these engines to anything else much of the memory they were using will not be freed and instead remain in the FastAllocator magazines.

While there are several ways to address this, the easiest way is for a storage server process to exit after closing a storage engine of one type and creating one of another type.

Start by tracing the StorageServer path that closes one storage engine and creates another, focusing on the Memory, SQLite, and Redwood engine transitions described in the issue. Verify the process-exit behavior after an engine switch and confirm that the change prevents memory from remaining allocated in FastAllocator magazines.

Written by the indexing model from the issue text.