New trait: UdpSplitMulticast

[ivmarkov]

Now that rs-matter had gained Groups support, we do need a way to join/leave Ipv6 multicast groups on a split-socket.

While for mDNS this was not necessary, as the socket can join the mDNS multicast group before it is split, the rs-matter groups' functionality demands dynamic multicast group join/leave while the socket is already split into a read + write halves and operating as such.

So in a way we need a new type of socket split that either:

• Still splits into a read + write halves, but the write half is not just UdpSend but also MulticastV4 and MulticastV6
• Or splits into (read, write, multicastv4, multicastv6) tuple

This PR implements the second approach, though for rs-matter specifically the first approach would work too.

[Copilot]

Pull request overview

Adds a new UDP splitting trait to support dynamic IPv4/IPv6 multicast join/leave operations after a socket has been split into independent halves (for group messaging scenarios such as Matter Groups).

Changes:

• Introduces UdpSplitMulticast and updates UdpConnect::Socket to require it.
• Implements UdpSplitMulticast for edge-nal-std::UdpSocket and edge-nal-embassy::UdpSocket, including multicast impls for &UdpSocket (embassy).
• Minor refactors/simplifications in mDNS broadcast iterator construction and HTTP server/task logic.

Reviewed changes

Copilot reviewed 6 out of 6 changed files in this pull request and generated 5 comments.

Show a summary per file

File	Description
edge-nal/src/stack/udp.rs	Adds UdpSplitMulticast and tightens UdpConnect::Socket bounds to require it.
edge-nal-std/src/lib.rs	Implements UdpSplitMulticast for the std UDP socket wrapper.
edge-nal-embassy/src/udp.rs	Implements UdpSplitMulticast for embassy UDP socket and adds multicast traits for &UdpSocket.
edge-mdns/src/io.rs	Simplifies IPv6 broadcast iterator chaining.
edge-http/src/lib.rs	Refactors chunked/HTTP1.0 validation into a guarded match arm.
edge-http/src/io/server.rs	Refactors acceptor loop to iterate signals instead of indexing.

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[Copilot]

Pull request overview

Copilot reviewed 7 out of 7 changed files in this pull request and generated 1 comment.

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