platform: Add UsePlatformWIFIMonitor to gRPC interface

Align dev-next-grpc with wip2 by adding UsePlatformWIFIMonitor()
to the new PlatformInterface, allowing platform clients to indicate
they handle WIFI monitoring themselves.

experimental/libbox/config.go

@@ -116,6 +116,10 @@ func (s *platformInterfaceStub) RequestPermissionForWIFIState() error {
 	return nil
 }
 
+func (s *platformInterfaceStub) UsePlatformWIFIMonitor() bool {
+	return false
+}
+
 func (s *platformInterfaceStub) ReadWIFIState() adapter.WIFIState {
 	return adapter.WIFIState{}
 }