CVE-2023-32058: Vyper vulnerable to integer overflow in loop

Due to missing overflow check for loop variables, by assigning the iterator of a loop to a variable, it is possible to overflow the type of the latter.

In the following example, calling test returns 354, meaning that the variable a did store 354 a value out of bound for the type uint8.

@external
def test() -> uint16:
x:uint8 = 255
a:uint8 = 0
for i in range(x, x+100):
a = i
return convert(a,uint16)

The issue seems to happen only in loops of type for i in range(a, a + N) as in loops of type for i in range(start, stop) and for i in range(stop), the compiler is able to raise a TypeMismatch when trying to overflow the variable.

thanks to @trocher for reporting