[ROS2] Startup Sequence

[amalnanavati]

The user needs a way to start the entire robot software from the app. This will be relevant for two scenarios:

1. when the user is starting a meal
2. if the e-stop is flipped, but either the system recovers (e.g., the F/T sensor resumes a stable connection) or the user deems it is safe (e.g., the user presses the hardware e-stop but at a later point wants to continue.)

To enable this, we should do the following:

1. Write an Ubuntu startup script that launches the web app and a flask server.
2. The web app should make one or more HTML calls to the flask server to launch all the required ROS components. The flask server should kill any previously running processes and start new ones.
3. In addition to displaying the watchdog status, the web app should display system diagnostic status from the flask server that monitors which nodes are running.

In this way, as long as the web app is running the user can start the whole system, and if the web app is not running (which is easy to detect) or the Flask server is not running (which we need to display to the user on the web app), the user has someone restart LoveLace and then it should be running.