Add a `resize()` function to `Primes<N>` that reuses the already computed primes.

[JSorngard]

Something like

impl<const N: usize> Primes<N> {
    pub fn resize<const M: usize>(self) -> Primes<M> {
       ... 
    } 
} 

[JSorngard]

May just implement a runtime sieve that starts out with a Primes<N> and then grows as needed.

[JSorngard]

Working on that in the extending_cache branch.