Adds Builder and VM Manager interfaces + implementation for UVM

[rawahars]

This pull request introduces a major refactor and formalization of the Utility VM (UVM) builder and management interfaces. It separates the responsibilities for VM configuration, host-side management, and guest-side actions into clear, testable layers. The changes include a new, well-documented builder interface, VM manager interface, concrete builder and VM manager implementations, along with comprehensive unit tests for the builder's functionality.

The most important changes are:

Architectural Refactor and Documentation

• Added a detailed README.md to the internal/vm package, clearly explaining the separation of concerns between the Builder, VM Manager, and Guest Manager layers, and documenting the responsibilities and flow for each layer.

Builder Interface and Implementation

• Replaced the old UVMBuilder interface with a new, comprehensive Builder interface in internal/vm/builder.go, providing modular access to memory, processor, NUMA, device, boot, and storage QoS configuration managers.
• Introduced a concrete implementation of the Builder interface in internal/vm/builder/builder.go for creating and configuring hcsschema.ComputeSystem documents.

VM Manager Interface and Implementation

• Created a new comprehensive UVM interface which corresponds to VM manager functionality.
• All the VM host side modification are responsibility of this interface.

Testing

• Added comprehensive unit tests for builder verification.

These changes establish a foundation for future VM configuration and management features.

[jterry75]

Seems like we should actually have the API for the PCI device, and then this one is actually add function

[jterry75]

This one is odd. If you had the VirtualMachineProcessor you would have already set its .Count/.Limit/,Weight and they would be in the builder right? Seems like if we need this overload we would want it to reflect a smaller set of just count/limit/weight overrides

[jterry75]

We should add this at the time of its use right? We dont want 9pfs if the caller has no shares right?

[rawahars]

IIRC these are added pre-emptively so that HCS can perform warm-up logic on its end.

[helsaawy]

can we have dedicated types for Windows and Linux builders and managers?
that way, we can specialize via function calls

type UtilityVM interface {
	BootOptions 
	DeviceOptions 
	// ...
}

type _ UtilityVM = &Linux 
type _ UtilityVM = &Windows

type Linux struct {
	builder
}

type Windows struct {
	builder
}

type builder struct {
	doc             *hcsschema.ComputeSystem
	assignedDevices map[hcsschema.VirtualPciFunction]*vPCIDevice
}

// ...

func (b *builder) SetUEFIBoot(bootEntry *hcsschema.UefiBootEntry) {
	// ...
}

func (b *Linux) SetLinuxKernelDirectBoot(options *hcsschema.LinuxKernelDirect) error {
	if osversion.Get().Build < 18286 {
		return errors.New("Linux kernel direct boot requires at least Windows version 18286")
	}
	uvmb.doc.VirtualMachine.Chipset.LinuxKernelDirect = options
	return nil
}

func (b *Windows) SetLinuxKernelDirectBoot(options *hcsschema.LinuxKernelDirect) error {
	return ErrUnsupportedOperation
}

// ...

[helsaawy]

i though vSMB was windows only?

[rawahars]

Yes vSMB is Windows only.

The idea of builder is to have a generic HCS Config builder. It's the responsibility of the caller i.e. VMController to configure the builder correctly.