[Polly] Remove PolyhedralInfo (#124437)
PolyhedralInfo is tied to the legacy pass manager. With the eventual
removal of the legacy pass manager it will not be useful anymore.
PolyhedralInfo was an experiment to make Polly's analysis available to
other passes. Its power is limited due to not being able to make
assumptions for which regular Polly would emit a runtime condition/code
versioning during optimization.
When eventually porting such an API to the new pass manager, we will
have to invent a new API.
