[InstructionSimplify] Extend simplifyICmpWithZero to handle equivalent zero RHS (#179055)

Add a new helper function `matchEquivZeroRHS()` that recognizes
comparisons with constants that are equivalent to comparisons with zero,
and transforms the predicate accordingly.

This handles the following transformations:
- icmp sgt X, -1 --> icmp sge X, 0
- icmp sle X, -1 --> icmp slt X, 0
- icmp [us]ge X, 1 --> icmp [us]gt X, 0
- icmp [us]lt X, 1 --> icmp [us]le X, 0

This enables more optimization opportunities in `simplifyICmpWithZero`,
such as folding icmp sgt X, -1 when X is known to be non-negative.

---

- IR Impact: https://github.com/dtcxzyw/llvm-opt-benchmark/pull/3414

GitOrigin-RevId: 85e07bad936360c52599863f0700008f9f304246