Add % operator logic to PyDough

[vineetg3]

The modulo (%) operator is used to calculate the remainder of a division operation between two numbers. For example:
A % B = R (where R is the remainder when A is divided by B). This issue would resolve just the support of % operator.

The general formula for % is:
remainder = a - (b * (quotient)).
The quotient depends on how division (a / b) is performed in the specific language (e.g., truncating or floor-based division)
When dealing with negative numbers:
In SQL, the modulo behavior is C++ like, where the result's sign matches the dividend, and the decimal part is truncated.
In Python, the result's sign matches the divisor, and the decimal part is rounded to negative infinity. Having the mod behave like Python simplifies mathematical operations, hence PyDough's implementation would be the same.

Here's a small table for clarification:

Comparison Between SQL, Python, and C++

Feature/Behavior	SQL (MOD() or %)	Python %	C++ %
Sign of Result	Matches the dividend	Matches the divisor	Matches the dividend
Division Behavior	Truncates toward 0	Floor division	Truncates toward 0
Formula	a - (a / b) * b	a - b * floor(a / b)	a - (a / b) * b
Examples (-10 % 3)	-1	2	-1
Examples (10 % -3)	1	-2	1
Examples (-10 % -3)	-1	-2	-1
Examples (10 % 3)	1	1	1

This feature needs to be documented in the function list documentation