Adds local model caching on docker container build

[CollectiveUnicorn]

• Adds local embedding model caching for chroma db on docker container build. This allows using the embedding function offline.
• Changes model to instructor-xl to match embeddings endpoint
• Disables chromadb telemetry that causes persistent errors when offline
• Sets env variables so that tiktoken with gpt-2 can be cached locally
• Adds parallel upload support via threading
• Persists db to local drive @ ~/.db/
• Adds initial tests