MDL-71264 behat: Change date(time) element update order
This includes 2 change to the order date(time) elements are filled,
each one addressing one type of problem, where current order is
problematic and can lead to unexpected dates.
1) Changing date, when current month only has X days and target
month has more than X days. Example, being 1 April, change
the date to 31 May.
This is solved by changing the order of introduction
from current D => M => Y to Y => M => D.
2) Changing date, when target month only has X days and current
month has more that X days. Example, being 31 March, change
the date to 28 Feb.
This is solved by always setting the D to 1, before the
Y => M => D sequence commented @ 1) begins.