- Add a more reliable heuristic for how long to run the CPU-side
  copy monitor.
- Check that copies sizes are appropriately divisible.
- Fix parsing issue for copies larger than 8192 GiB.
- Clean up, and document bugs in, the time synchronization code.
- Wait for user before logging copies.

Performing the synchronization in a child process was fragile,
high-overhead, and unnecessary for our use cases.

Avoids incorrectly interpreting CUDA Driver Library error codes as
though they were CUDA Runtime Library error codes (the numbering is
similar, but not identical).

Also cleans up how we initialize and terminate a context for
capability checking in `mon_cross_ctx_copies`.

On-GPU copy monitoring may have been disfunctional on Maxwell-.

No longer requires a recompile to change the number or type of copy
monitoring threads.

Benchmark supports:
=> Generating parallel copies from CPU to GPU in seperate process
=> Granular timestamping of when each portion of the copy completes
=> Monitoring of copy process from either CPU or GPU
=> Tested on platforms including the GV100 and GV11B

Formerly known as diff_ctx_diff_stream.

*** Warning ***
* The current implementation requires some hardcoded parameters
* (such as the number of monitoring threads on the GPU) to be
* updated and recompiled when switching test platform.
***