GeezerVison

A random find from my side, I was going through this code when I noticed
some unnecessary conversions happening.

Nice performance improvement basically for free (numbers from my M1 Pro
laptop):

    In [1]: from ipaddress import IPv4Address, IPv6Address

    In [2]: v4 = IPv4Address('10.0.0.1')

    In [3]: IPv6Address(f'::ffff:{v4}') == IPv6Address((0xffff << 32) + v4._ip)
    Out[3]: True

    In [4]: %timeit IPv6Address(f'::ffff:{v4}')
    3.63 µs ± 12 ns per loop (mean ± std. dev. of 7 runs, 100,000 loops each)

    In [5]: %timeit IPv6Address((0xffff << 32) + v4._ip)
    184 ns ± 0.413 ns per loop (mean ± std. dev. of 7 runs, 10,000,000 loops each)