Benchmarks Create Device When Enumerating Test Cases

[cwfitzgerald]

Currently all of our gpu-enabled tests intentionally do not create devices while trying to enumerate the available tests. We should make sure that all the benchmarks also do this. The idea is to make enumerating tests as fast as possible, as it needs to be done on every single test run, no matter how many actual tests are enabled. This is why we use a .gpuconfig file that is generated ahead of time