Add setMonthYear support for multi-calendar

[mathewepstein]

Is your feature request related to a problem? Please describe.
With a multi calendar, when a selected date causes the max date to change, I am unable to focus the second calendar on the new max date

Describe the solution you'd like
Allow setMonthYear to accept the calendar index to focus on a month/year for a specified calendar

Describe alternatives you've considered
I could change the multi-calendar solo option to false, but this forces the two calendars to show the same month/year which is a worse user experience when selecting large date ranges