Reintroduce multirobot launch files with updates to TB3 with Harmonic

[SteveMacenski]

Requires https://github.com/ros-navigation/nav2_minimal_turtlebot_simulation/pull/11

• [x] update tests for .xacro

[mergify[bot]]

This pull request is in conflict. Could you fix it @SteveMacenski?

[codecov[bot]]

Codecov Report

All modified and coverable lines are covered by tests :white_check_mark:

see 4 files with indirect coverage changes