[VPlan] Also print final VPlan directly before codegen/execute. (#82269)

Some optimizations are apply after UF and VF have been chosen. This
patch adds an extra print of the final VPlan just before
codegen/execution.

In the future, there will be additional transforms that are applied
later (interleaving for example).

PR: https://github.com/llvm/llvm-project/pull/82269