[llvm] [LV] Support EVL for partial reduction and VPExpressionRecipe. (PR #205741)

[Elvis Wang via llvm-commits]

ElvisWang123 wrote:

Gentle ping! 
Could @fhahn and @lukel97 help clarify the preferred direction here? We have conflicting suggestions on whether to implement EVL transformations for ExpressionRecipes in VPlanTransforms or VPExpressionRecipe. 
I am happy to implement either approach.

https://github.com/llvm/llvm-project/pull/205741