Resolve "adhoc_storage instances should keep track of jobs using them"

This MR associates registered adhoc storage instances with registered jobs.

To do so, it modifies both the job_manager and the adhoc_storage_manager classes to store shared_ptrs to admire::internal::job_info and admire::internal::adhoc_storage_info records. This allows returning the pointers when checking for information as well as modifying the records in a synchronized manner.

To keep track of adhoc_storage usage, the new internal adhoc_storage_info type includes a std::shared_ptr<job_info> m_client field that models the association. As of today, an adhoc storage instance can only have a single job client associated. Trying to add more will result in error.

Closes #85 (closed) #86 (closed) #88 (closed)