Backend-defined Dependencies

[joeyballentine]

Mostly finished. I just need to review everything because I'm sure I left tons of commented-out code everywhere and probably just need to clean stuff up as well. But functionally its working.

This PR defines dependencies on the backend side. This means dependencies are linked directly to a package now.

The python process also installs all the core dependencies itself through pip commands in a subprocess. This allows someone to run the backend remotely and still have all the core deps be installed. The core deps just get auto-installed the way they did before.

run.py now contains some imports that are required to be in that order. Basically, it imports the stuff that checks and installs the dependencies before doing anything else. It also force installs sanic, sanic-cors, and semver before doing any others.

This also implements the nvml python package to check for an nvidia GPU on the backend side rather than on the frontend. this allows us to do the same GPU checks as before, only without needing to search for nvidia smi.

What this doesn't have is the ability to install optional dependencies through the backend. I'll do that in a separate PR.

[joeyballentine]

TLDR: TODO is to clean up come comments and unused code. I also need to test what happens on a fresh start.

[joeyballentine]

So this has an issue: Starting up the backend for the first time takes some time due to the deps being installed. I'm not really sure what to do about that, since we time out the backend if it doesn't respond within a certain time. gonna have to think about this a bit