Resolve pernicious race between destructor and thread functions by insisting that destructor is invoked after the class has gone back to being a harmless single-threaded thing.

I also added some unrequested const's

Revive it in tests as well

- make the directory structure match the package structure
- sanitize the package structure (test --> testing)
- add auto-detection of proto file dependencies

Remove some unused options and make server_threads relevant
Start stubbing out better qps/core calculations

reset option to the mark, create a closed loop config params (empty
message) for consistency with other tests.