[roll] Roll fuchsia [net-types] Make GenericOverIp type explicit

Requires that #[derive(GenericOverIp)] invocations explicitly specify
which type parameter is the generic-over-ip one with the
`#[generic_over_ip]` attribute, rather than inferring it from the bounds
on the struct generics.

Consider the following example:

```
 #[derive(GenericOverIp)]
 #[generic_over_ip(<ARGUMENTS EXPLAINED BELOW>)]
 struct Foo<T>(T);
```

`#[generic_over_ip(T, Ip)]` specifies that the GenericOverIp impl
should be written treating `T` as an `Ip` implementor (either `Ipv4` or
`Ipv6`).

`#[generic_over_ip(T, IpAddress)]` specifies that `T` is an `IpAddress`
implementor (`Ipv4Addr` or `Ipv6Addr`).

`#[generic_over_ip(T, GenericOverIp)]` specifies that `T` implements
`GenericOverIp<I>` for all `I: Ip`. (Notably, we'd like to use this case
for the Ip and IpAddress cases above, but we cannot due to issues
with conflicting blanket impls.)

`#[generic_over_ip()]` specifies that `Foo` is IP-invariant.

Original-Reviewed-on: https://fuchsia-review.googlesource.com/c/fuchsia/+/919652
Original-Revision: bc20a8f309a53612d98c49301250a34bac34a3f4
GitOrigin-RevId: e72b15ee906daabb61ef58f3ffdd8326626bb9dd
Change-Id: I287700977c17944dffd6cd6f8e1e15fb62bb5473