Update/enhance architecture documentation

[weeco]

The architecture documentation helped me understanding how Cortex works. However while working on the deployment of Cortex I noticed there may be some parts which have not been documented yet or left out (for a reason?).

1. Configs Deployment

I am not sure what this deployment is supposed to do or how it interacts with the other microservices. Apparently it has another dependency on a Database (Postgres only?).

2. Table Manager

Same here, what is this microservice responsible for? Do I need it when I want to use Cassandra/BigTable instead of DynamoDB?

3. Ruler

Is the Ruler dependency required to run Cortex? In case I do not want to use any of the alert manager features.

[stale]

This issue has been automatically marked as stale because it has not had any activity in the past 30 days. It will be closed in 7 days if no further activity occurs. Thank you for your contributions.

[pracucci]

Closed by #1421 and #1945.