Create find_previous_power_of_two.py (#11004)

* Create find_previous_power_of_two.py

* [pre-commit.ci] auto fixes from pre-commit.com hooks

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* Update find_previous_power_of_two.py

This change avoids the unnecessary left shift operation

* Update find_previous_power_of_two.py

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Co-authored-by: pre-commit-ci[bot] <66853113+pre-commit-ci[bot]@users.noreply.github.com>
Co-authored-by: Christian Clauss <[email protected]>