Add Multi-Process Sharding Support

Created by: VelvetThePanda

Summary

This should make multi-process sharding just that much easier.

Details

Adds a new client and configuration option to support multi-process sharding

Changes proposed

• Unseal DiscordShardedClient
• Add some private protected access modifiers where needed
• Add a new client type (DiscordClusterClient)
• Changed ShardedLoggerFactory to be generic (to support correct contextual logging)
• Added ClusterId and ShardBootCount properties to DiscordConfiguration

Notes

How have we gone over half a decade without this being a thing?