[llvm] [VPlan] Retain exit conditions and edges in initial VPlan (NFC). (PR #137709)

[via llvm-commits]

================
@@ -541,8 +541,9 @@ void VPlanTransforms::prepareForVectorization(VPlan &Plan, Type *InductionTy,
   //    Thus if tail is to be folded, we know we don't need to run the
   //    remainder and we can set the condition to true.
   // 3) Otherwise, construct a runtime check.
-
   if (!RequiresScalarEpilogueCheck) {
+    if (LatchExitVPB)
----------------
ayalz wrote:

```suggestion
    if (auto *LatchExitVPB = MiddleVPBB->getSingleSuccessor())
```
?

https://github.com/llvm/llvm-project/pull/137709