[LV] Always create VPWidenCanonicalIVRecipe, optimize away later.

This patch updates createBlockInMask to always generate
VPWidenCanonicalIVRecipe and adds a transform to optimize it away later,
if it is not needed.

This is a step towards breaking up VPWidenIntOrFpInductionRecipe and
explicitly distinguishing between vector phis and scalarizing.

Split off from D116123.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D117140