[llvm] [LSR] Recognize vscale-relative immediates (PR #88124)

[Graham Hunter via llvm-commits]

huntergr-arm wrote:

Added some new test cases and converted the checks to look at llc output, since it's easier to see what the impact is. I think the cost comparison changes will also be required to get the best results here, as there's still some problems with the many_mulvl1_addressing output.

https://github.com/llvm/llvm-project/pull/88124