[llvm] [LV][VPlan] Extract the implementation of transform Recipe to EVLRecipe into a small function. NFC (PR #119510)

[Florian Hahn via llvm-commits]

================
@@ -1438,13 +1438,105 @@ void VPlanTransforms::addActiveLaneMask(
     HeaderMask->replaceAllUsesWith(LaneMask);
 }
 
+// Convert each widen Recipe to a widen EVLRecipe in VectorLoopRegion.
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fhahn wrote:

```suggestion
// Try to convert \p CurRecipe to a corresponding EVL-based recipe. Returns nullptr if no EVL-based recipe could be created.
```

https://github.com/llvm/llvm-project/pull/119510