Many bug fixes in the assistants, ctrl_cascaded_pids, ctrl_utils, teleop, tutorial packages

Fixed a buggy loop condition
Fixed syntax errors in python and launch files
Improved and refactored parts of the code

Update CI workflow with a scheduled event

Massive code cleanup

Add a Github Action for continuous integration tests

Minor changes in gazebo_ros_plugins to display more information during the tests

Centralize time handling

Migrated the gazebo worlds launch files to the new sim time system