[EuiDatePicker] Display error for minDate and maxDate

[tabna]

In the date picker, if you set a minDate and maxDate, the < > controls enable and disable appropriately, but the Month and Year controls do not.

For example, in the demo shown in the documentation, the min/max is currently set to a one week time span, 1/20/2020 - 2/6/2020. If you click on '2020' in the calendar header, it displays a blank screen where normally you would see the year choices. At the very least, it should display all allowed years within the min/max - in this case, just 2020. What would be better is that if only the current year is allowed, the '2020' link is disabled.

Also in the demo, if you click on the Month, you get a screen showing all month choices. You should only see months within the allowed range. If the range spans multiple years, you'd still see all months, but in the demo it only spans two months of one year, so you should only see January and February.

Because of this, I am able to select a date not in the range by clicking on 'February', then clicking on 'May', which because today was the 1st, populates the input with 5/1/2020, well outside of the range.