Loki: Add minimal distributed mode support

Currently we only support and test Monolithic and Simple Scalable modes for Loki.

This issue is to add additional support for Loki Distributed, which has been requested several times over the years as a feature by our community.

NOTE: At the time of writing we still do not formally test or run our pipelines with Loki distributed, this is experimental and should be treated as such.

• Update overview.md doc with information on deployment modes and how to enable them
• Ensure warning remains in-place when loki-distributed is enabled
• Make the proper configuration changes to support loki distributed
• Ensure Loki distributed works with istio service mesh
• Update log forwarders to point to proper Loki microservice when distributed is enabled