fix potential infinite loop in string_builder and list

[lenawanel]

this would happen if the minimum length requested by the _grow_by
function was the highest power of 2 a usize could store.
So i.e. if a usize was 8bits of length you could have:

new_cap = 1;
while new_cap <= `0b10000000` {
	new_cap = new_cap << 1; // the highest new_cap can reach here is
				// 0b10000000 since anything higher overflows to 0
				// thus never not satisfying the loop condition and infinitely looping
}