Add multiplier support to ForceTorqueSensorBroadcaster (backport #1647)

[mergify]

Summary:
This PR introduces a new multiplier parameter set for the force_torque_sensor_broadcaster controller. Users can now specify per–axis scaling factors for both force and torque readings, applied after the existing offset logic. This feature enables dynamic unit conversions or gain adjustments without modifying downstream code.

Changes:

• Extended the auto‑generated Params to include multiplier.force.{x,y,z} and multiplier.torque.{x,y,z}
• Implemented apply_sensor_multiplier(...) and invoked it in the publish loop immediately after offset application
• Added a new gtest (SensorName_Publish_Success_with_Multipliers) mirroring the offset test to verify correct scaling in both the published message and exported state interfaces

Pipeline Status:
✅ All existing and new tests pass locally (colcon test --packages-select force_torque_sensor_broadcaster)
✅ pre-commit run shows no formatting errors

Testing:

• Unit test covers positive, negative, and zero multipliers
• Manual verification in a running ROS 2 system confirms expected behavior

  ---

  This is an automatic backport of pull request Add multiplier support to ForceTorqueSensorBroadcaster #1647 done by Mergify.

[mergify]

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Changes to be committed:
	modified:   force_torque_sensor_broadcaster/include/force_torque_sensor_broadcaster/force_torque_sensor_broadcaster.hpp
	modified:   force_torque_sensor_broadcaster/src/force_torque_sensor_broadcaster.cpp
	modified:   force_torque_sensor_broadcaster/src/force_torque_sensor_broadcaster_parameters.yaml
	modified:   force_torque_sensor_broadcaster/test/test_force_torque_sensor_broadcaster.cpp

Unmerged paths:
  (use "git add <file>..." to mark resolution)
	both modified:   doc/release_notes.rst

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