[llvm] [NewPM] Remove LowerWidenableConditionLegacyPass (PR #72818)

[Aiden Grossman via llvm-commits]

boomanaiden154 wrote:

This should be the last removal in the current iteration of legacy pass removals (other than maybe `LoopGuardWideningLegacy`). There are some other passes that look like they could be removed:
* CFGOnlyPrinterLegacy
* CFGOnlyViewerLegacy
* CFGViewerLegacy
* CallGraphPrinterLegacy
* InstCountLegacy
* LoopExtractorLegacy
* PlaceBackedgeSafepointsLegacy
* PredicateInfoPrinterLegacy
* RegToMemLegacy
* StripGCRelocatesLegacy

A lot of these are utility functions used manually with `opt`, so I'm not sure we should look into removing most of them yet. There are a couple in there that look like they just need a bit more untangling to remove.

https://github.com/llvm/llvm-project/pull/72818