WSD API migration to gRPC

[atharvasaraf123]

Migrates the Key Manager Daemon (WSD) from a manual REST-only HTTP multiplexer to a fully typed, high-performance Dual-Socket Architecture supporting both gRPC and REST JSON clients simultaneously using grpc-gateway.

Changes Made:
Dual Unix Domain Socket Support: The daemon now securely listens on two distinct endpoints (-grpc.sock and standard .sock), allowing native gRPC traffic to process without overhead while routing conventional REST requests via a reverse proxy.
Backward-Compatible JSON: Configured runtime.JSONPb with UseProtoNames: true to guarantee pristine snake_case key serialization matching legacy API outputs.
Robust Error & Validation Handling: Upgraded endpoint errors to status.Errorf to correctly map bad requests to HTTP 400/404 REST codes.

Changes in the API:

1. Successful post on destroy used to return 204(StatusNoContent), now returns 200(StatusOK).
2. Valid endpoint using an unsupported HTTP method now returns 501 (StatusNotImplemented), instead of 405(StatusMethodNotAllowed).

New Autogenerated files:
api_grpc.pb.go - Provided with RegisterWorkloadServiceServer
api.pb.gw.go - Provided with RegisterWorkloadServiceHandler

Testing:
Added UTs for GRPC apis
All existing UTs along with workload passes

[NilanjanDaw]

We should also close the HTTP endpoint.

[atharvasaraf123]

We are doing s.httpServer.Shutdown below in the function.

[atharvasaraf123]

/gcbrun

[NilanjanDaw]

I see a few of the schema cloudbuild tests are failing, which means we are diverging from the current API behavior. Can you please check once.

[atharvasaraf123]

@NilanjanDaw @atulpatildbz do we also want to remove this check? If we remove this, then we will get a 501 (StatusNotImplemented) instead of 405 (StatusMethodNotAllowed).

[NilanjanDaw]

Instead of a per-function validate call which will require us to manually add these checks, can we add a central validator to automatically validate everything?
Something like

// ValidationInterceptor validates incoming protobuf requests before they reach the handler.
func ValidationInterceptor(validator *protovalidate.Validator) grpc.UnaryServerInterceptor {
	return func(ctx context.Context, req interface{}, info *grpc.UnaryServerInfo, handler grpc.UnaryHandler) (interface{}, error) {
		if msg, ok := req.(proto.Message); ok {
			if err := validator.Validate(msg); err != nil {
				return nil, status.Errorf(codes.InvalidArgument, "validation failed: %v", err)
			}
		}
		return handler(ctx, req)
	}
}

and then wire it up in the newserver

// In NewServer:
validator, err := protovalidate.New()
if err != nil {
    return nil, fmt.Errorf("failed to initialize protovalidate: %w", err)
}
grpcServer := grpc.NewServer(
    grpc.UnaryInterceptor(ValidationInterceptor(validator)),
)

[NilanjanDaw]

@atulpatildbz how is the limit and offset working here? does this mean we only return the first 100 keys?