feat(dns): Implement resolving /dnsaddr for wasm target

[dariusc93]

Description

This PR introduces a libp2p-dns-websys, largely inspired by libp2p-dns internals, allowing the client to resolve /dnsaddr as well as /dns{4,6} (for webrtc since this transport for webrtc-websys doesnt resolve or utilize/dns* but expects a /ip*) using DoH (DNS-over-HTTPS). By default, it uses cloudflare endpoint to resolve the DNS but can use a custom endpoint.

Resolves #5531.

AI Assistance Disclosure

Tools used (required — write none if no AI was used): none

Attestation (required):

• I have read every line of this diff, understand what it does, and can explain it in review.

Notes & open questions

1. While this is a separate crate to keep the same pattern as we have done for other respected transports, should this remain separate or should be move it to be apart of libp2p-dns instead?
2. Should we rely on a different endpoint by default?
3. Does it make sense to be more protocol-aware in regards to webrtc (or webrtc-direct) or should we also have the protocol handle/resolve /dns* and leave this crate to only resolve /dnsaddr?

Change checklist

• I have performed a self-review of my own code
• I have made corresponding changes to the documentation
• I have added tests that prove my fix is effective or that my feature works
• A changelog entry has been made in the appropriate crates