Add GetUtf8Name and upgrade v1.0.3

[prozolic]

This PR adds GetUtf8Name method that returns the enum definition name in UTF8 bytes (ReadOnlySpan<byte>).

public abstract record IpAddr
{
    [MethodImpl(MethodImplOptions.AggressiveInlining)]
    public static ReadOnlySpan<byte> GetUtf8Name(IpAddr ipaddr)
    {
        return ipaddr switch
        {
            V4 => "V4"u8,
            V6 => "V6"u8,
            None => "None"u8,
            _ => []
        };
    }
}