parameter_overrides() returns an empty vector

Bug report

The parameter_overrides method of NodeOptions returns an empty vector.

Required Info:

• Operating System: Ubuntu 20.04
• Installation type: binary
• Version or commit hash: galactic
• Client library (if applicable): rclcpp

Steps to reproduce issue

1. modify the set_and_get_parameters example to print the size of the parameter_overrides in the SetAndGetParameters constructor:

std::cout << "overrides: " << options.parameter_overrides().size() << std::endl;

2. run the node with an override parameter: ros2 run demo_nodes_cpp set_and_get_parameters --ros-args -p foo:=42

Expected behavior

The parameter remapping (override) foo:=42 should appear in the vector returned by the parameter_overrides().

Actual behavior

parameter_overrides() returns an empty vector.