DecimalValue checked_add should not upcast to i256 unconditionally

[joseph-isaacs]

vortex/vortex-array/src/scalar/typed_view/decimal/dvalue.rs

Line 133 in bf61c07

fn checked_binary_op<F>(&self, other: &Self, op: F) -> Option<Self>

Find the max size of left and right and use that.

This just hides an upcast which can lead to other large scalar for no reason.