[VPlan] Convert to concrete recipes before dissolving loop regions. NFCI (#141999)

After updating #118638 on tip of tree, expanding
VPWidenIntOrFpInductionRecipes fails because it needs the loop region to
get the latch to insert the increment into:

VPBasicBlock *ExitingBB =
Plan->getVectorLoopRegion()->getExitingBasicBlock();
Builder.setInsertPoint(ExitingBB,
ExitingBB->getTerminator()->getIterator());
    auto *Next = Builder.createNaryOp(AddOp, {Prev, Inc}, Flags,
WidenIVR->getDebugLoc(), "vec.ind.next");

However after #117506, the region is dissolved so it doesn't work.

This shuffles the dissolveLoopRegions steps to be after
convertToConcreteRecipes so we can use the region when expanding
VPWidenIntOrFpInductionRecipes

Author: lukel97

llvm/lib/Transforms/Vectorize/LoopVectorize.cpp

@@ -7289,14 +7289,14 @@ DenseMap<const SCEV *, Value *> LoopVectorizationPlanner::executePlan(
       TTI.getRegisterBitWidth(TargetTransformInfo::RGK_FixedWidthVector));
   VPlanTransforms::removeDeadRecipes(BestVPlan);
 
+  VPlanTransforms::convertToConcreteRecipes(BestVPlan,
+                                            *Legal->getWidestInductionType());
   // Retrieve and store the middle block before dissolving regions. Regions are
   // dissolved after optimizing for VF and UF, which completely removes unneeded
   // loop regions first.
   VPBasicBlock *MiddleVPBB =
       BestVPlan.getVectorLoopRegion() ? BestVPlan.getMiddleBlock() : nullptr;
   VPlanTransforms::dissolveLoopRegions(BestVPlan);
-  VPlanTransforms::convertToConcreteRecipes(BestVPlan,
-                                            *Legal->getWidestInductionType());
   // Perform the actual loop transformation.
   VPTransformState State(&TTI, BestVF, LI, DT, ILV.AC, ILV.Builder, &BestVPlan,
                          OrigLoop->getParentLoop(),