Enable neural network tests on ROCm
Enable NN tests to run on ROCm by using XLA implementation instead of
cuDNN (which is NVIDIA-only) and fixing compute capability skip checks.
Changes:
- testScaledMatmul: skip compute capability check on ROCm (works on ROCm)
- testScaledDotGeneral: skip compute capability check on ROCm (works on ROCm)
- testDotProductAttention: add ROCm skip for cuDNN impl (XLA impl still runs)
- testDotProductAttentionMask: use XLA instead of cuDNN on ROCm
- testDotProductAttentionBiasGradient: use XLA instead of cuDNN on ROCm
