Implemented a controller coordinator (backport #63)

[mergify]

Changes Made

This PR implements a coordinator to manage activating and deactivating controllers using a single endpoint. This feature is motivated by the desire to launch controllers in a single launch file, but waiting to activate them until a future point. Such a scenario occurs when you want to switch back and forth between a company-provided control system and a custom control system.

Testing

Tested using the BlueROV2 Heavy and in simulation using Blue

---

This is an automatic backport of pull request #63 done by [Mergify](https://mergify.com).

[mergify]

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Changes to be committed:
	new file:   controller_coordinator/CHANGELOG.md
	new file:   controller_coordinator/CMakeLists.txt
	new file:   controller_coordinator/LICENSE
	new file:   controller_coordinator/README.md
	new file:   controller_coordinator/package.xml
	new file:   controller_coordinator/src/coordinator.cpp
	new file:   controller_coordinator/src/coordinator.hpp
	new file:   controller_coordinator/src/coordinator_parameters.yaml

Unmerged paths:
  (use "git add/rm <file>..." as appropriate to mark resolution)
	deleted by us:   auv_control_demos/CHANGELOG.md
	both modified:   auv_control_demos/package.xml
	deleted by us:   auv_control_msgs/CHANGELOG.md
	both modified:   auv_control_msgs/package.xml
	deleted by us:   auv_controllers/CHANGELOG.md
	both modified:   auv_controllers/package.xml
	deleted by us:   controller_common/CHANGELOG.md
	deleted by us:   controller_common/package.xml
	deleted by us:   end_effector_trajectory_controller/CHANGELOG.md
	deleted by us:   end_effector_trajectory_controller/package.xml
	deleted by us:   ik_solvers/CHANGELOG.md
	deleted by us:   ik_solvers/package.xml
	deleted by us:   thruster_allocation_matrix_controller/CHANGELOG.md
	both modified:   thruster_allocation_matrix_controller/package.xml
	deleted by us:   thruster_controllers/CHANGELOG.md
	both modified:   thruster_controllers/package.xml
	deleted by us:   topic_sensors/CHANGELOG.md
	deleted by us:   topic_sensors/package.xml
	deleted by us:   velocity_controllers/CHANGELOG.md
	both modified:   velocity_controllers/package.xml
	deleted by us:   whole_body_controllers/CHANGELOG.md
	deleted by us:   whole_body_controllers/package.xml

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