[llvm] [LV] Run VPlan licm late in executePlan (PR #181122)

[Andrei Elovikov via llvm-commits]

https://github.com/eas commented:

I'm not familiar with this code, so don't expect any formal approval/changes requested from me. However, trying to be useful:

1) Updated commit message is much better, thanks.
2) Seems all RISC-V (and at least some AArch64) are `vscale`-related. Any chance we should be emitting better code from the start without relying on a separate `LICM`?
3) See inline comment.

https://github.com/llvm/llvm-project/pull/181122