[Data] Compute Expressions - Expr Arithmetic

[zzchun]

Description

Completing the Expr Arithmetic operations: negate, sign, power, abs

import ray
from ray.data import from_items
from ray.data.expressions import col

ds = from_items([{"x": 5}, {"x": 2}, {"x": 0}])
for row in ds.iter_rows():
    print(row)

x_expr = col("x")

ds = ds.with_column("x_negate", x_expr.negate())

ds = ds.with_column("x_sign", x_expr.sign())

ds = ds.with_column("x_power", x_expr.power(2))

ds = ds.with_column("x_abs", x_expr.abs())

for row in ds.iter_rows():
    print(row)

Related issues

Related to #58674

[gemini-code-assist]

Code Review

This pull request introduces several new arithmetic helper expressions (negate, sign, power, abs) to ray.data.expressions.Expr, along with corresponding unit tests. The implementation is clean and follows the existing pattern for PyArrow compute function wrappers. The tests are well-structured and cover the new functionality. I have a couple of suggestions to improve safety and code clarity.

[zzchun]

Hi @richardliaw , could you please review this PR when you have a moment? Thanks!