[fix] Handle non-primitives in isNumber (#12034)

While investigating https://github.com/chartjs/chartjs-plugin-zoom/issues/928, I found that `isNonPrimitive` will throw TypeError on a Moment.js object after it's passed through Chart.js's options proxy, because the object has its `Symbol.toPrimitive`, `toString`, and `valueOf` all set to null.

(See https://developer.mozilla.org/en-US/docs/Web/JavaScript/Reference/Global_Objects/String#string_coercion for background reading.)

Since isNumber appears to be a low-level function that can take any arbitrary input, it seems worth letting it handle this case.