[VPlan] Manage compare predicates in VPRecipeWithIRFlags.

Extend VPRecipeWithIRFlags to also manage predicates for compares. This
allows removing the custom ICmpULE opcode from VPInstruction which was a
workaround for missing proper predicate handling.

This simplifies the code a bit while also allowing compares with any
predicates. It also fixes a case where the compare predixcate wasn't
printed properly for VPReplicateRecipes.

Discussed/split off from D150398.

Reviewed By: Ayal

Differential Revision: https://reviews.llvm.org/D158992