std::move within a copy constructor (on a data member that isn't
mutable) will always result in a copy. Because of that, the behavior of
this copy constructor is identical to the one that would be generated
automatically by the compiler, so we can remove it.
Like with CPU emulation, we generally don't want to fire off the threads
immediately after the relevant classes are initialized, we want to do
this after all necessary data is done loading first.
This splits the thread creation into its own interface member function
to allow controlling when these threads in particular get created.
Since C++17, the introduction of deduction guides for locking facilities
means that we no longer need to hardcode the mutex type into the locks
themselves, making it easier to switch mutex types, should it ever be
necessary in the future.
The pusher instance is only ever used in the constructor of the
ThreadManager for creating the thread that the ThreadManager instance
contains. Aside from that, the member is unused, so it can be removed.
