Replace Launch Files with Main Files that Configure and Activate

[zeerekahmad]

We want to simplify and remove launch files that may be overkill for such small repos and add main files. Since it's already composable, we can add the node separately anyways.

What if you separate it out into main.cpp and do the lifecycle bringup there? The launch file feels super unnecessary here for a single node

Originally posted by @troygibb in #8 (comment)