Overflow safety in duration unit classes

[erikc5000]

For the most part, Island Time detects and throws an exception on overflow, like java.time does. The unit classes are a bit inconsistent in that they aren't overflow safe by default.

Consider IntHours:

val totalHours = Int.MAX.hours + 1.hours // overflow
val minutes = Int.MAX.hours.inMinutes // overflow
val minutes2 = Int.MAX.hours.inMinutesExact() // exception

Internally, we have plusExact and minusExact infix functions to do overflow safe math. The question is whether or not these should be the default and instead, require a plusWithOverflow, minusWithOverflow, or inMinutesWithOverflow. I'm leaning "yes", but curious to hear if others have an opinion on this.

On native, it seems like LLVM's UBSan could be used to detect overflow during debug as a possible alternative, though not sure if enabling it is possible with Kotlin Native. Doesn't help with JVM though, obviously.