Refactor launch file system to be more composable / easy to configure in different environments

[oswinso]

One issue that's been annoying is that when switching between different environments (ie. gazebo vs bagfile for puck vs others potentially), that a lot of the configs need to be manually changed (i.e lidar topic, 3d mode for mapper) etc. One thing that would be nice would be to have a system (using launch files or env variables) that could set the various configurations depending on which environment we were in, so that we don't need to change those every time, saving time with debugging when something doesn't work.

Kind of related to #104.