[Relax][ONNX] Preserve bool dtype when folding constant comparisons

[StrongbodyStrongmind]

Fixes #20282.

The ONNX frontend constant-folds binary operators with NumPy. When both
operands have the same dtype, the result was unconditionally cast back to
the operand dtype to avoid NumPy precision widening.

This is correct for arithmetic operations, but incorrect for comparison
operators such as Less, LessOrEqual, Greater, and GreaterOrEqual,
whose result dtype must be bool.

As a result, constant-folded comparisons produced correct 0/1 values but
returned int32 or float32 tensors instead of bool.

This patch preserves NumPy boolean results while keeping the existing
no-widening behavior for non-boolean binary operations.

Tests:

• Added regression coverage for constant-folded ONNX comparisons with
  int32 and float32 operands.
• The 8 new cases fail before the fix and pass after it.
• Related ONNX binary tests: 16 passed.
• git diff --check upstream/main..HEAD: passed.