[llvm] [LV] Use ExtractLane(LastActiveLane, V) live outs when tail-folding. (PR #149042)

[David Sherwood via llvm-commits]

david-arm wrote:

The difference between the title of the PR and the commit message is a bit confusing, i.e. sometimes refers to LastActiveLane and sometimes to FirstActiveLane. Perhaps worth making consistent?

https://github.com/llvm/llvm-project/pull/149042