feat(transport): Add GlobalOnly Transport implementation

[tcoratger]

Description

Upstreams the GlobalOnly transport from @mxinden's kademlia-exporter to rust-libp2p.

Source: https://github.com/mxinden/kademlia-exporter/blob/master/src/exporter/client/global_only.rs.

Resolves: #3669.

Notes & open questions

The Rust is_global() function associated to Ipv4Addr and Ipv6Addr used in this implementation is unstable.

• Rust issue: Tracking issue for Ipv{4,6}Addr convenience methods rust-lang/rust#27709

The method chosen here is to include the implementation of is_global() directly to the library to secure its implementation while waiting for the Rust issue to be resolved. The is_global() is then constructed to refer to all addresses that are not contained in the following Special-Purpose Address lists:

• ipv4: https://www.iana.org/assignments/iana-ipv4-special-registry/iana-ipv4-special-registry.xhtml#note2
• ipv6: https://www.iana.org/assignments/iana-ipv6-special-registry/iana-ipv6-special-registry.xhtml

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• A changelog entry has been made in the appropriate crates

[thomaseizinger]

Thanks! I left some comments.

[mxinden]

Thank you for the work here @tcoratger!

[thomaseizinger]

Apart from one unresolved conversation, this looks good to me!

[thomaseizinger]

Can you address the clippy and doc test failures? I think then we can merge this 🥳

[tcoratger]

Can you address the clippy and doc test failures? I think then we can merge this 🥳

@thomaseizinger Done

[thomaseizinger]

Thank you!

[mxinden]

🙏 thanks @tcoratger. Upgraded downstream user mxinden/kademlia-exporter#292.