[llvm] [VPlan] Expand VPWidenIntOrFpInductionRecipe into separate recipes (PR #118638)

[Nikolay Panchenko via llvm-commits]

npanchen wrote:

> Although I just want to double check, I was thinking that doing the regular widening for now would still be correct. Can we convert it to VP intrinsics as a separate task after the EVL transform or is it needed for correctness?

I don't think regular widening of these inductions (i.e. without EVL) will be correct. The main problem is vsetvl's  6.3.2 so that if increment is VLMAX, last two iteration may result to overincrement.
fyi: QEMU has special [`rvv_vl_half_avl`](https://lists.nongnu.org/archive/html/qemu-devel/2024-08/msg01060.html) option to properly test 6.3.2

https://github.com/llvm/llvm-project/pull/118638