consomme: add udp timeout

[damanm24]

This PR addresses one of the backlog items in #2313 regarding: leaking connection state.

[Copilot]

Pull request overview

This PR implements idle timeout functionality for UDP connections in the consomme network device to prevent connection state leaks. The timeout defaults to 5 minutes per RFC 4787 and can be configured through ConsommeParams.

Key changes:

• Added configurable UDP connection timeout with RFC 4787-compliant default
• Implemented last activity tracking per UDP connection
• Added timeout checking logic during connection polling to remove stale connections

Reviewed changes

Copilot reviewed 2 out of 2 changed files in this pull request and generated no comments.

File	Description
vm/devices/net/net_consomme/consomme/src/udp.rs	Adds timeout parameter to Udp struct, tracks last_activity timestamp per connection, and implements timeout checking logic in poll_udp
vm/devices/net/net_consomme/consomme/src/lib.rs	Adds udp_timeout field to ConsommeParams with 5-minute default per RFC 4787 and passes timeout to Udp::new()

[github-actions]

At least one Petri test failed.

[chris-oo]

Looks reasonable but is there any way to unittest this with a configured shorter timeout?

[damanm24]

@chris-oo The testing story for consomme, at this point is not great. So unfortunately there's no way to unittest this change at this time. One of the backlog items includes addressing this gap, but it requires a larger change.