Nightly CUDA test takes too long

[msaroufim]

Right now the test is exceeding the default timeout period of 60 min. This doesn't feel great and there's some simple solutions

1. Parallel tests
2. Automated sharing tests
3. Manually sharded tests

We tried 1 and 2 in the past before and both of them gave surprising results so 3 feels like the most natural thing to do for me