This will correct/switch "year" unit diffing from the current integer
subtraction to a crono subtraction. Consequently, two dates are (at
least) one year apart now if (at least) a full calendar year separates
them. The previous implementation simply subtracted the year part of the
dates.
Note: this parts with ES SQL's implementation of the same function,
which itself is aligned with MS SQL's implementation, which works
equivalent to an integer subtraction.
Fixes#112482.
