Account for bool being passed.
calendar_links and calendar_link both allow for mixed parameters to be passed as $all_day; however $all_day is ran through getBoolean() at line 82 of CalendarLinkTwigExtension.php.
Since mixed is allowed, an int may be passed in and fail at 163 $this->getString(). For instance if an int of 0 or 1 is passed, it will fail.
This addition checks in getBoolean() for an int and casts it to a bool... which I think works in all scenarios.
There are some edge cases. If a negative number is passed it will return allday as true; otherwise under normal entries it should be fine. 0 will return false and anything else will return true.
We can account for a negative number if we want, but if someone put a negative number into calendar_links, they deserve a whitescreen.
Closes #3284487