Keep the saturate attribute when constant folding rewrites CastLike to Cast

[Mohammed Alkindi (MohammedAlkindi)]

The CastLike partial evaluator rewrites CastLike to Cast without its saturate attribute, so saturate=0 silently becomes the default 1. For a float8 target, values out of range then clamp to ±448 instead of becoming NaN. ONNX Runtime on CastLike <saturate = 0> to float8e4m3fn with input [1000, 1, -1, 0.3]:

original   [nan, 1, -1, 0.3125]
optimized  [448, 1, -1, 0.3125]

The rewrite now forwards saturate, which is what ONNX's CastLike function body passes on to Cast, including an @sat reference inside a function. round_mode is not forwarded, matching that body; one test checks it stays off the Cast.

Three of the four new tests fail before the change. onnxscript/optimizer: 78 passed, and the optimized models give the same ONNX Runtime output as the originals for saturate=0, round_mode="down" and the @sat function. ruff check and ruff format --check are clean.