[ROCm] support benchmark flag for MIOpen (#77438)
Fixes #68172. Generally, this corrects multiple flaky convolution unit test behavior seen on ROCm.
The MIOpen integration has been forcing benchmark=True when calling `torch._C._set_cudnn_benchmark(False)`, typically called by `torch.backends.cudnn.set_flags(enabled=True, benchmark=False)`. We now add support for MIOpen immediate mode to avoid benchmarking during MIOpen solution selection.
Pull Request resolved: https://github.com/pytorch/pytorch/pull/77438
Approved by: https://github.com/ngimel, https://github.com/malfet
