Add missing bridges for simulation time (backport #443)

[mergify]

We need a parameter bridge for receiving the simulation time in the ROS world.

Some of them got (accidentally?) removed with #266, others never had the bridge.

Fixes #439

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This is an automatic backport of pull request #443 done by Mergify.

[mergify]

Cherry-pick of 301ca58 has failed:

On branch mergify/bp/humble/pr-443
Your branch is up to date with 'origin/humble'.

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Changes to be committed:
	modified:   gz_ros2_control_tests/tests/position_test.py
	modified:   ign_ros2_control_demos/launch/ackermann_drive_example.launch.py
	modified:   ign_ros2_control_demos/launch/cart_example_effort.launch.py
	modified:   ign_ros2_control_demos/launch/pendulum_example_effort.launch.py
	modified:   ign_ros2_control_demos/launch/pendulum_example_position.launch.py

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   gz_ros2_control_demos/launch/cart_example_position.launch.py
	deleted by us:   gz_ros2_control_demos/launch/cart_example_velocity.launch.py
	deleted by us:   gz_ros2_control_demos/launch/diff_drive_example.launch.py
	deleted by us:   gz_ros2_control_demos/launch/gripper_mimic_joint_example_effort.launch.py

To fix up this pull request, you can check it out locally. See documentation: https://docs.github.com/en/pull-requests/collaborating-with-pull-requests/reviewing-changes-in-pull-requests/checking-out-pull-requests-locally