NumericLimits<u32>::max + 1 overflowing to 0 caused us to call
AK::get_random_uniform(0) which doesn't make sense (the argument is an
_exclusive_ bound).
unsigned_int(0) doesn't need to draw bits from RandomnessSource.
An expression for getting INT_MAX for u32 didn't need to be
special-cased over the general formula.
This is a follow-up on a few comments
These functions all plug into RandomnessSource and produce random values
of various types. They are to be used either inside other generator
definitions or inside the GEN(...) macro when used in tests.
