This change better aligns gpu-microbench with the assumptions of
the cuda_scheduling_examiner Makefile.

=> Uploads a large texture to the GPU on every frame
=> Requires the freeglut library (freeglut3-dev on Ubuntu)
=> Due to special requirements, not built by default
=> Written for Anderson and Bakita RTAS'24 paper

To specify a custom path to nvcc when building:
`make NVCC=/my/path/to/nvcc`

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.
***

Benchmark supports:
=> Looping on the GPU for a specified number of iterations
=> Looping infinitely on the GPU
=> Logging the sum time (ns and ms) for all iterations to complete

Also splits `testbench.h` out of `copy_testbench.h` for use in other
benchmarks.

Benchmark supports:
=> Generating a chain of copies in a single context
    - No timing pause between copies
=> Copies to, from, or between device(s)
=> Variable size and number of copies
=> Logging how many milliseconds each copy takes

*** Warning ***
* Relies on implicit synchronization of unidirectional copies across
* streams. Verify that this is still the case with CUDA before
* trusting results. One can check by verifying that the runtime for
* one iteration roughly matches the time for each iteration in a
* multi-iteration run.
***