[-Wunsafe-buffer-usage] Use `Strategy` to determine whether to fix a parameter

- Use Strategy to determine whether to fix a parameter
- Fix the `Strategy` construction so that only variables on the graph
are assigned the `std::span` strategy

Reviewed by: t-rasmud (Rashmi Mudduluru), NoQ (Artem Dergachev)

Differential revision: https://reviews.llvm.org/D157441