[Polly] Improve Simplify pass PM integration.

1. LegacyPM: Rename SimplifyLegacyPass to SimplifyWrapperPass.
2. LegacyPM: Complete create/init functions in LinkAllPasses.h
3. NewPM: Only invalidate non-Scop passes if changed.
4. NewPM: Add to default pass pipeline.
5. NewPM: Print -analyze header for each print<polly-simplify>