Add latestCommittedWriteRegion ReadConsistencyStrategy

## Summary

The CosmosClient instance should be able to route read requests to the write region and perform quorum reads against that write region.

## Details

Add a new `latestCommittedWriteRegion` value to the `ReadConsistencyStrategy` enum that:
- Routes read requests to the current write region
- Performs quorum reads against that write region
- Ensures reads reflect the latest committed writes

## Motivation

This enables strong consistency reads by targeting the write region directly, avoiding cross-region replication lag.