Function pathCompare

Compares two string arrays and returns a comparison result.

The algorithm is as follows:

1. Check if either value is undefined. If both are undefined, return 0. If a is undefined, return 1. If b is undefined, return -1.
2. Check the lengths of the arrays. If they are different, return the difference.
3. Check the cumulative lengths of the arrays using the count of UTF-16 units in each string. If they are different, return the difference.
4. Check the individual elements of the arrays via lexical comparison. If they are different, return the difference.
5. If all elements are the same ("deep equality"), return 0.