[shimV2] added network controller implementation

[rawahars]

Summary

This change adds the network controller implementation for V2 shims which manages the network lifecycle for a single pod running inside a UVM. The implementation provides a clear lifecycle state machine, separates platform-specific logic for LCOW and WCOW. This controller will be initialized from VMController which can inject the low-level managers to perform VM host + guest network operations.

The main changes are grouped below.

Network controller implementation:

• Implemented the Controller interface and its concrete Manager type, providing Setup and Teardown methods to manage HCN namespaces and endpoints for a pod (internal/controller/network/interface.go, internal/controller/network/network.go).

Platform-specific guest operations:

• Added platform-specific files for LCOW and WCOW, implementing guest-side network namespace and endpoint management with proper separation via build tags (internal/controller/network/network_lcow.go, internal/controller/network/network_wcow.go).

Lifecycle state management:

• Defined a State type to track the network lifecycle, including transitions for setup, teardown, and error handling (internal/controller/network/state.go).

[helsaawy]

if we are going to gate the Controller functionality by build tags, can we fully extend it to the GuestNetworkManager types?
that way we don't have to deal with unused fields in either case:

//
// internal/controller/network/network.go 
//

type Controller struct {
	// ...

	// guestMgr manages the guest-side NIC operations.
	guestMgr guestNetworkManager

	// ...
}

// New creates a ready-to-use Controller in [StateNotConfigured].
func New(
	vmNetManager vmNetworkManager,Expand commentComment on line R51Resolved
	guestMgr guestNetworkManager,
) *Controller {

//
// internal/controller/network/network_lcow.go 
//

// guestNetworkManager exposes linux guest network operations.
// Implemented by [guestmanager.Guest].
type guestNetworkManager interface {
	// AddLCOWNetworkInterface adds a network interface to the LCOW guest.
	AddLCOWNetworkInterface(ctx context.Context, settings *guestresource.LCOWNetworkAdapter) error
	// RemoveLCOWNetworkInterface removes a network interface from the LCOW guest.
	RemoveLCOWNetworkInterface(ctx context.Context, settings *guestresource.LCOWNetworkAdapter) error
}

//
// internal/controller/network/network_wcow.go 
//

// guestNetworkManager exposes windows guest network operations.
// Implemented by guestmanager.Guest.
type guestNetworkManager interface {
	// AddNetworkNamespace adds a network namespace to the WCOW guest.
	AddNetworkNamespace(ctx context.Context, settings *hcn.HostComputeNamespace) error
	// RemoveNetworkNamespace removes a network namespace from the WCOW guest.
	RemoveNetworkNamespace(ctx context.Context, settings *hcn.HostComputeNamespace) error
	// AddNetworkInterface adds a network interface to the WCOW guest.
	AddNetworkInterface(ctx context.Context, adapterID string, requestType guestrequest.RequestType, settings *hcn.HostComputeEndpoint) error
	// RemoveNetworkInterface removes a network interface from the WCOW guest.
	RemoveNetworkInterface(ctx context.Context, adapterID string, requestType guestrequest.RequestType, settings *hcn.HostComputeEndpoint) error
}

[helsaawy]

also, more of a nit, but can WCOW be the default and therefore have LCOW require the lcow build tag?

[rawahars]

@helsaawy Made the suggested changes. These changes are inline with other places now.
Please take a look.

[helsaawy]

why did we go with not go with WCOW being the default?
it will likely cause more problems that the default build fails during runtime rather than assuming WCOW

[rawahars]

Right that was the intention based on discussion with Justin.
LCOW shim needs to be specifically compiled using lcow tag and WCOW with wcow. There's no default otherwise.

[helsaawy]

so just building a shim will always give us something entirely non-functional?

[rawahars]

Yes that's true! It's purely intent driven with new shim.