[thanos] - create dedicated code_suggestions hashring route

What

Creates a dedicated hashring config route for code_suggestions

Why

We are about to enable remote-write for some of our production environments, which means stepping these over to the new receivers.
However this could introduce problems with our existing data, as we will be duplicating it via remote-write while we test.
So by creating a dedicated temporary route for code_suggestions, we can start sending data from production environments without needing to add them to the queriers.
This enables us to test querying the data from staging before doing a cut over.