Introduce sharding rules to MongoDB collections

[hackerwins]

Description:

This description is written by @sejongk

To address the load concentrated on the database, we need to introduce a MongoDB Sharded Cluster and apply appropriate sharding rules to the collections for a solution.

• Indexes: https://github.com/yorkie-team/yorkie/blob/main/server/backend/database/mongo/indexes.go
• Note: https://codepair.yorkie.dev/khfbyv

Why:

The Yorkie cluster stores almost all data, including documents and changes representing edits, in MongoDB. It has been observed that in real-world service scenarios, the majority of the load is concentrated on the database rather than the application servers, as was the case with Yorkie's predecessor, Kaleido.

[sejongk]

We need to determine which sharding method is appropriate for Yorkie and what kinds of sharding method MongoDB supports.
For example, ranged sharding would be efficient if a range of documents is frequently queried. Additionally, hash sharding would be ideal for massively-scalable workloads because it distributes data evenly.