Implement the rest of the Task trait

[Mossaka]

I am creating this issue to track the remaining rpcs in the Task trait that containerd-shim-wasm hasn't implemented yet. Some are worth to implement and others aren't (like ResizePty). I am particularly interested to see Stats being implemented so that the shim could return the cgroup stats of a running container back to containerd.

The Task service

// Shim service is launched for each container and is responsible for owning the IO
// for the container and its additional processes.  The shim is also the parent of
// each container and allows reattaching to the IO and receiving the exit status
// for the container processes.
service Task {
	rpc State(StateRequest) returns (StateResponse);
	rpc Create(CreateTaskRequest) returns (CreateTaskResponse);
	rpc Start(StartRequest) returns (StartResponse);
	rpc Delete(DeleteRequest) returns (DeleteResponse);
	rpc Pids(PidsRequest) returns (PidsResponse);
	rpc Pause(PauseRequest) returns (google.protobuf.Empty);
	rpc Resume(ResumeRequest) returns (google.protobuf.Empty);
	rpc Checkpoint(CheckpointTaskRequest) returns (google.protobuf.Empty);
	rpc Kill(KillRequest) returns (google.protobuf.Empty);
	rpc Exec(ExecProcessRequest) returns (google.protobuf.Empty);
	rpc ResizePty(ResizePtyRequest) returns (google.protobuf.Empty);
	rpc CloseIO(CloseIORequest) returns (google.protobuf.Empty);
	rpc Update(UpdateTaskRequest) returns (google.protobuf.Empty);
	rpc Wait(WaitRequest) returns (WaitResponse);
	rpc Stats(StatsRequest) returns (StatsResponse);
	rpc Connect(ConnectRequest) returns (ConnectResponse);
	rpc Shutdown(ShutdownRequest) returns (google.protobuf.Empty);
}

from https://github.com/containerd/containerd/blob/main/api/runtime/task/v2/shim.proto#L29C3-L51

What's missing from containerd-shim-wasm

• state()
• create()
• start()
• delete()
• pids() → return all pids inside the container
• pause() -> pauses the container process
• resume() -> resumes the container process
• Implement checkpoint() from Task trait #222
• kill()
• exec() → execute additional process inside the container
• resize_pty() → ResizePty resizes the processes pty/console
• Implement close_io() from Task trait #223
• update() → update task settings
• wait()
• Implement Stats() from Task trait #208
• connect()
• shutdown()