Add LCOW live migration support across the controller stacks

[rawahars]

Implement end-to-end live migration support for LCOW pods so a running guest and its workloads can be moved between hosts. Every controller in the stack — VM, pod, Linux container, process, network, and SCSI/Plan9/VPCI devices — gains a save/import lifecycle plus the destination-side patch and resume plumbing needed to rebind local resources and bring the workload back online.

Migration lifecycle:

• Source: Save serializes a controller's state into a self-describing protobuf envelope and freezes the controller (StateSourceMigrating) so no mutating ops race the transfer; Resume rolls the freeze back, and a finalize Stop or VM teardown terminates it.
• Destination: Import rehydrates a controller into a migrating state, Patch repoints saved resources (layer VHDs, process IO/bundle, network namespace) at the destination host, and Resume binds the live VM, guest, and devices and republishes events so containerd treats the task as locally running. AbortMigrated discards an imported-but-never-resumed controller and emits synthetic exits so Delete can proceed.

VM controller:

• Add the source/destination migrating states and the full HCS migration lifecycle: InitializeLiveMigrationOnSource, StartLiveMigrationOnSource, StartLiveMigrationTransfer, FinalizeLiveMigration, plus StartWithMigrationOptions on the destination.
• Exchange the opaque compatibility blob, retain the final HCS document so the destination can recreate an identical VM, and recover the GCS port/bridge-id allocator floors so reissued ids cannot collide.
• Make SCSI initialization lazy (built on first use from the HCS document) and handle never-started/destination teardown paths, including the already-stopped HCS error.

Controller-specific changes:

• SCSI controller switches to an RWMutex and rejects all ops while migrating; ReserveForRootfs now carries the full disk config.
• Process, network, container, and VM state machines document and enforce the new migrating states and transitions.
• Pod gains a migrating guard, AbortMigrated fan-out, and routes new containers through lazy SCSI init.

Includes accompanying unit tests for the new save/import/patch/resume paths across all controllers.