Check for presuppositions in `calendar-date-is-valid-p'

Check for presuppositions in `calendar-date-is-valid-p'

Do not signal an error in `calendar-date-is-valid-p' if passed a
value which is not a three-element list of integers.  Signaling
an error makes the function unusable as a predicate for valid
date values. (Bug#74848)
* lisp/calendar/calendar.el (calendar-date-is-valid-p): Add the
check that input is a 3-element list.
* test/lisp/calendar/calendar-tests.el: New file with tests.

(cherry picked from commit 77f73abd92f1a627ddec0648dcfe14e56b525f4d)