consomme: add support for dns over tcp

[damanm24]

This PR adds support for DNS over TCP.

If a TCP connection is being initiated (by the guest), addressed to consommé's gateway IP on port 53, consommé's TCP module will intercept the request and instead of creating a socket on the host it will submit the DNS query on behalf of the guest using the resolver implementation that was introduced in #2633.

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⚠️ Unsafe Code Detected

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[Copilot]

Pull request overview

This PR adds DNS over TCP support to the consomme network stack, complementing the existing DNS over UDP functionality introduced in PR #2633. When a guest initiates a TCP connection to the gateway IP on port 53, consomme intercepts the connection and handles DNS queries using platform-specific system resolvers (DnsQueryRaw on Windows, res_nsend on Unix) instead of creating a real host socket.

Changes:

• Implements virtual TCP DNS handler that processes DNS queries over TCP without real sockets
• Adds TCP transport support to platform-specific DNS resolver backends (RES_USEVC flag for Unix, DNS_PROTOCOL_TCP for Windows)
• Refactors DNS backend to use Arc instead of Box to enable sharing between UDP and TCP handlers

Reviewed changes

Copilot reviewed 8 out of 8 changed files in this pull request and generated 3 comments.

Show a summary per file

File	Description
vm/devices/net/net_consomme/consomme/src/lib.rs	Defines DNS_PORT constant at crate level for reuse
vm/devices/net/net_consomme/consomme/src/udp.rs	Updates UDP DNS handler to include transport type in DnsFlow
vm/devices/net/net_consomme/consomme/src/tcp/ring.rs	Removes test-only attribute from is_empty() method (now used in production)
vm/devices/net/net_consomme/consomme/src/tcp.rs	Adds TcpBackend enum, DNS TCP connection handling, and poll_dns_backend method
vm/devices/net/net_consomme/consomme/src/dns_resolver/mod.rs	Adds DnsTransport enum and changes backend from Box to Arc for sharing
vm/devices/net/net_consomme/consomme/src/dns_resolver/dns_tcp.rs	New module implementing DNS TCP framing and message handling per RFC 1035
vm/devices/net/net_consomme/consomme/src/dns_resolver/windows/mod.rs	Adds DNS_PROTOCOL_TCP support to Windows resolver backend
vm/devices/net/net_consomme/consomme/src/dns_resolver/unix/glibc.rs	Adds RES_USEVC flag support for TCP queries and refactors ResState structure

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At least one Petri test failed.

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At least one Petri test failed.