Avoid changing the current cudnn.benchmark value

[carmocca]

What does this PR do?

Re-land of #12020
Fixes #12713

Does your PR introduce any breaking changes? If yes, please list them.

Benchmark now defaults to False, as it was in v1.5

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cc @justusschock @kaushikb11 @awaelchli @Borda @rohitgr7 @akihironitta

[carmocca]

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