Changes and corrections to support ROS 2 Galactic

[gbiggs]

This PR provides the fixes necessary to compile and run with ROS 2 Galactic.

This PR is backwards-compatible with ROS 2 Foxy. It can be merged without impacting support for ROS 2 Foxy.

Part of open-rmf/rmf#60.

[codecov]

Codecov Report

Merging #23 (56785e3) into main (e711737) will not change coverage.
The diff coverage is n/a.

@@           Coverage Diff           @@
##            main     #23     +/-   ##
=======================================
  Coverage   0.00%   0.00%             
=======================================
  Files         90      46     -44     
  Lines       7480    3752   -3728     
=======================================
+ Misses      7480    3752   -3728     

Flag	Coverage Δ
tests	0.00% <ø> (ø)

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
...f_simulation/rmf_building_sim_common/src/utils.cpp
...uilding_sim_gazebo_plugins/src/toggle_charging.cpp
..._sim_common/include/rmf_robot_sim_common/utils.hpp
...building_sim_common/src/crowd_simulator_common.cpp
...rmf_building_sim_common/crowd_simulator_common.hpp
.../rmf_simulation/rmf_robot_sim_common/src/utils.cpp
...ation/rmf_robot_sim_common/src/ingestor_common.cpp
...ation/rmf_robot_sim_common/src/ingestor_common.cpp
...f_simulation/rmf_building_sim_common/src/utils.cpp
...tion/rmf_robot_sim_gazebo_plugins/src/readonly.cpp
... and 122 more

[marcoag]

LGTM!