[release/2.4][ROCm][TunableOp] Fix TunableOp warmup environment variable. (#147412)

[naromero77amd]

This PR corrects the behavior of the TunableOp warmup variables:

PYTORCH_TUNABLEOP_MAX_WARMUP_DURATION_MS
PYTORCH_TUNABLEOP_MAX_WARMUP_ITERATIONS

See the updated comments which describe how the environment variables are intended to work. Previously, if you only set one of the two environment variables the warmup iters would always be zero.

Manually tested the four possible combinations to make sure things still behavior as intended.

Pull Request resolved: https://github.com/pytorch/pytorch/pull/147412 Approved by: https://github.com/jeffdaily

(cherry picked from commit 4b35139a462f1858cf5fe5346e16f7e1abede78d)

[naromero77amd]

This is a subtle bug that has been present for a while. I discovered it post PyTorch 2.6 release. Cherry picked from upstream and will need to be cherry picked into ROCm 2.5 and 2.6 release branches.

[rocm-repo-management-api[bot]]

Jenkins build for a9992d4cd7685b64a1ca9c419925b6bcd19de1ef commit finished as SUCCESS Links: Blue Ocean view / Build artifacts

[rocm-repo-management-api[bot]]

Jenkins build for a9992d4cd7685b64a1ca9c419925b6bcd19de1ef commit finished as FAILURE Links: Blue Ocean view / Build artifacts

[naromero77amd]

!cherry-pick --onto release/2.5

[rocm-mici]

Created branch autogenerated/release/2.5_cherry-pick_pr-2017 and https://github.com/ROCm/pytorch/pull/2040

[naromero77amd]

!cherry-pick --onto release/2.6

[rocm-mici]

Created branch autogenerated/release/2.6_cherry-pick_pr-2017 and https://github.com/ROCm/pytorch/pull/2042