feat: add list api

[edwinkys]

Purpose

This API introduces a new API to the Collection as defined below. This API will return all of the records contain in the collection in the form of a HashMap of the Vector ID as a primitive type of usize and Record which contains vector and metadata.

pub fn list(&self) -> Result<HashMap<usize, Record>, Error> {...}

Approach

Currently, this adds a very barebone approach of doing this without other utility functionality like pagination or return limit.

Testing

• I have tested this PR locally.
• I added tests to cover my changes, if not applicable, I have added a reason why.

I have added a test for each cargo test and pytest to test this implementation.

Chore checklist

• I have updated the documentation accordingly.
• I have added comments to most of my code, particularly in hard-to-understand areas.