Fix some Calendar layout glitches on "hover" on iOS.

:hover rules on iOS (and android?) are problematic.  In addition to activating 300ms
after touching an element (whereas really they shouldn't activate at all), often the
wrong element gets the effect.  Therefore:

1. Leverage _CssStateMixin for Calendar drop down.  It's already being included for Calendar anyway.
2. Limit the :hover pattern for Calendar days to CalendarLite widget, not Calendar widget

Fixes #17814, refs #12276.