fixes: slow listing of collections, pass an optional embedding_function

[blob42]

• avoids unecessary fallback to the default embedding function

Description of changes

Summarize the changes made by this PR.

• Improvements & Bug fixes
  • pass an optional embedding_function to list_collections to avoid the slow fallback to default embeddings.

Test plan

• Before this fix, listing collections is slow even when using other embedding functions like OpenAI's one.
• With this fix, if the embedding function is passed, listing collections is instant.

[naynaly10]

Is it bad practice to store the API Key (for an embedding function) in the database?

[blob42]

@jeffchuber Do you think this can be reviewed/merged ? it would greatly improve the speed of listing collections and does not break the original signature.

[jeffchuber]

@HammadB was this addressed in another way?

[jeffchuber]

We need to rethink this from first principles. One stop-gap may be to change list_collections send back a list of strings.