[llvm] [LV] Move 3 functions into VPlanTransforms (NFC) (PR #158644)

[Ramkumar Ramachandra via llvm-commits]

artagnon wrote:

> > @artagnon looks there a test failures with expensive checks which looks related to the patch: https://lab.llvm.org/buildbot/#/builders/187/builds/12178.
> > Is it possible that some stale code got moved?
> 
> Hm, that's strange: I thought there were no conflicts. Taking a look.

Ugh, it looks like runPass runs verifyVPlanIsValid when expensive checks are enabled:

```cpp
    bool Res = Transform(Plan, Args...);
    if (VerifyEachVPlan)
      verifyVPlanIsValid(Plan);
    return Res;
```

... should we just update the tests?

https://github.com/llvm/llvm-project/pull/158644