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

[Nikita Popov via llvm-commits]

nikic wrote:

> 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.

I think at least the printing passes should get migrated to `print<foo>` NewPM passes.

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