[Polly][ScopInfo] Lazy Scop instantiation (#179535)

The old NPM was using ScopInfo pass introduced in
https://reviews.llvm.org/D20962, which in contrast to the LPM was using
ScopInfoRegionPass. ScopInfo was instantiating all Scop objects
immediately. After codegenning, all Scop objects need to be recomputed
anyway, making this approach wastful. The PhaseManager inherited this
behaviour from the NPM, leading to some concerns.

Replace the instantiate-all behavior of ScopInfo with an on-demand
instantiation. SCoPs now must be iterated using ScopDetection instead
using ScopInfo, but only some unsed legacy NPM passes (now removed) were
doing that anyway.

GitOrigin-RevId: d5607ad55c5e56383d33e6ec0f582a687d75dedb