[ENH] Schema helpers for rust client (#5707)

## Description of changes

_Summarize the changes made by this PR._

- Improvements & Bug fixes
    - N/A
- New functionality
    - Mirrors the python schema impl:
        - Implement `Schema::create_index`
        - Implement `Schema::delete_index`
        - Implement `IndexConfig`, which is a enum covering all index configs

## Test plan

_How are these changes tested?_

- [ ] Tests pass locally with `pytest` for python, `yarn test` for js, `cargo test` for rust

## Migration plan

_Are there any migrations, or any forwards/backwards compatibility changes needed in order to make sure this change deploys reliably?_

## Observability plan

_What is the plan to instrument and monitor this change?_

## Documentation Changes

_Are all docstrings for user-facing APIs updated if required? Do we need to make documentation changes in the_ [_docs section](https://github.com/chroma-core/chroma/tree/main/docs/docs.trychroma.com)?_

Author: Sicheng-Pan