Migration to LLVM's NewPM

[vchuravy]

Since https://twitter.com/ryan_levick/status/1443202538099073027?s=21 has spurred some interest in the community,
I wanted to publicly track where we are at in transitioning from the old pass manager to the new pass manager.

• Transition our passes to work with the NewPM
  • AllocOpt Make AllocOpt NewPM compatible #44273
  • DemoteFloat16 [LLVM][PM] Make LowerSIMDLoop NewPM compatible #40884
  • FinalGCLowering [LLVM] Convert more passes to NewPM #42463
  • GCInvariantVerifier Make another wave of passes NewPM compatible #44276
  • JuliaLICM [LLVM] Convert more passes to NewPM #42463
  • LateLowerGCFrame [LLVM] Convert more passes to NewPM #42463
  • LowerExcHandlers Make another wave of passes NewPM compatible #44276
  • CombineMulAdd [LLVM][PM] Make LowerSIMDLoop NewPM compatible #40884
  • MultiVersioning Make another wave of passes NewPM compatible #44276
  • PropagateJuliaAddrspaces Make more passes NewPM compatible #44277
  • LowerPTLS Make another wave of passes NewPM compatible #44276
  • RemoveJuliaAddrspaces Make more passes NewPM compatible #44277
  • RemoveNI [LLVM][PM] Make LowerSIMDLoop NewPM compatible #40884
  • LowerSIMDLoop [LLVM][PM] Make LowerSIMDLoop NewPM compatible #40884
• Prototype a pipeline build on the NewPM Transition pipeline to NewPM #44365
  • expose as a development option
• Ensure compatibility with LLVM.jl and wider ecosystem like GPUCompiler/Enzyme that run custom passes
• Acceptance testing for new pipeline
  • Performance
  • Correctness
  • Compiler performance

The most tedious aspect right now is doing the API change to our passes, and after that the real work can get started.

[vchuravy]

Now done as part of #48700