Use nebula for model inference

[nchapman]

The first version of nebula is nearly ready to integrate. Here are some of the things we need to do.

• [x] Integrate nebula into the project using cargo git reference
• [x] Create nebula plugin with javascript API
• [x] Replace llamafile with new nebula plugin API
• [x] Make sure nebula builds on all platforms via CI
• [x] Figure out how to handle GPU support during builds

[Warefoxe]

@ospfranco please check my fork https://github.com/Warefoxe/pulsar for 1,2 part of this

[ospfranco]

Please open a PR