[X86] Fold `(icmp ult (add x,-C),2)` -> `(or (icmp eq X,C), (icmp eq X,C+1))` for Vectors

This is undoing a middle-end transform which does the opposite. Since
X86 doesn't have unsigned vector comparison instructions pre-AVX512,
the simplified form gets worse codegen.

Fixes #66479

Proofs: https://alive2.llvm.org/ce/z/UCz3wt

Closes #84104
Closes #66479