Clean vsock sockets after krunkit exit

[unsuman]

Fixes #101

Note: AI was used to assist with the development of this PR

[gemini-code-assist]

Code Review

This pull request introduces a cleanup mechanism for vsock socket files by implementing a VsockCleanupGuard that handles both normal exits and SIGINT signals via the ctrlc crate. The changes include a new cleanup module and a vsock_socket_paths method in KrunContext to identify files for removal. The reviewer suggested refactoring the timesync socket path generation into a helper method to eliminate code duplication and improve maintainability.

[gemini-code-assist]

The logic for generating the timesync socket path is duplicated here and in the TryFrom<Args> for KrunContext implementation (lines 205-208). Refactoring this into a helper method improves maintainability and ensures consistency across the codebase. Please also update the usage in the TryFrom implementation to use this new method.

    fn timesync_socket_path() -> PathBuf {
        PathBuf::from(format!(
            "/tmp/krunkit_timesync_{}.sock",
            std::process::id()
        ))
    }

    /// Collect all vsock socket paths that should be cleaned up on exit.
    pub fn vsock_socket_paths(&self) -> Vec<PathBuf> {
        let mut paths = Vec::new();
        for device in &self.args.devices {
            if let VirtioDeviceConfig::Vsock(vsock) = device {
                paths.push(vsock.socket_url.clone());
            }
        }
        if self.args.timesync.is_some() {
            paths.push(Self::timesync_socket_path());
        }
        paths
    }