Embeddings Service

[jac]

Adds Embeddings service for Cody embeddings (disabled by default)

• SG blobstore + external storage supported by setting .Values.embeddings.backend to appropriate values
  • Updates env vars on both the embeddings container and worker container.
  • Doesn't set on frontend despite being mentioned in docs as consensus is it's not actually needed on frontend (happy to be proven wrong)

Checklist

• Follow the manual testing process
• Update changelog

Test plan

Tested locally using blobstore + gcs (using EMBEDDINGS_UPLOAD_GOOGLE_APPLICATION_CREDENTIALS_FILE_CONTENT)

• Successfully created embeddings for repositories

[unknwon]

Can't really review much but if it works then it's great, as long as it can be used to replaced the current Cloud-specific version (so we don't end up maintaining two charts of embeddings :D