Add ROS 2 control mock hardware mode

[Daniiiil1]

Summary

Add a use_mock_hardware parameter to the odrive_ros2_control system interface so controllers can be developed and tested without SocketCAN or physical ODrives.

Behavior

• skips CAN and node-ID requirements in mock mode
• initializes deterministic zero state instead of NaN
• mirrors position commands into position state
• integrates velocity commands into position using the ROS control period
• models effort-only control as a locked axis with zero velocity
• preserves velocity and effort feed-forward state when those interfaces accompany a primary command
• keeps the existing real-hardware path unchanged

The README documents the parameter and model. This implements the behavior outlined by the maintainer in #24.

Validation

• git diff --check
• reviewed every lifecycle path to ensure mock configure, cleanup, activation, deactivation, read, write, and mode switching avoid SocketCAN access

A full build requires the repository ROS 2 development container and is left to project CI.

Closes #24

[CLAassistant]

All committers have signed the CLA.

[samuelsadok]

There's one thing I missed when writing the comment in #24 (comment): There is already a vendor independent ROS2 way to do this: mock_components/GenericSystem.

This repo already showcases it in the odrive_botwheel_explorer usage example, in diffbot.ros2_control.xacro.

With this in mind, do you still have a use case where mock support directly in odrive_hardware_interface.cpp would be important? (please describe)

Still added some review comments while I was at it.

[samuelsadok]

the body of this for loop should be in a separate function, e.g. Axis::update_mock()

[samuelsadok]

hardware_interface::parse_bool() seems to be the standard way to do this.

[samuelsadok]

This adds more complexity than necessary to the init logic. Note that we can just construct the Axis objects with {nullptr, 0} if use_mock_hardware_ is true. Could be as simple as:

use_mock_hardware_ = // load from params
if (use_mock_hardware_) {
    // fill axes_ array with Axis(nullptr, 0)
} else {
    // old instantiation logic
}