CNCF - Cortex: Switch Cortex Ruler to query Query Frontend

Description: Cortex Ruler queries ingester directly for rule evaluation. This is okay but if Cortex Ruler could query Query Frontend instead for rule evaluation, it can benefit from more features in the Query Frontend like vertical sharding. This also simplifies the Cortex ruler to not embed a querier and uses less resources. For this project, we would like to switch Cortex Ruler to query Query Frontend. You are expected to work with a microservice architecture and write unit tests and end to end tests to make sure the feature works correctly.

Expected Outcome: Cortex Ruler talks to Query Frontend for rules evaluation.