Panic if an allocation would exceed isize::MAX bytes

[rtfeldman]

Our pointers can only index up to isize::MAX into an array because they do signed pointer arithmetic.

This means a List, Str, Dict, or Set must never exceed isize::MAX bytes of capacity, and should panic if they are about to, as the alternative would be undefined behavior. Notes:

• This is bytes, not elements.
• We should do this "overflow" check on all operations that can increase capacity, e.g. append, prepend, concat, reserve, withCapacity, etc.
• We should also give a compile-time error if a list literal or string literal would be too big.

[rtfeldman]

Closing in favor of #3299