[ENH] Add new internal spann config nreplica_count to limit number of centers considered on write (#5313)

## Description of changes

This PR adds a new internal spann config field called nreplica_count to
limit the number of centers considered on write. this has been validated
to decrease write time significantly by modifying write nprobe to be 8,
and we saw compaction time decrease from 560mins to 224min.

## 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)?_