Allow index to exist and be maintained without being used in production queries

I suspect very heavily that we are going to have customers who want to have a primary or other index on their production dataset for the purpose of BI tools, customer service queries (to find and fix errors, etc), and other reasons. On the other hand, our recommendations are to never have a primary index since you wouldn't want a production query to accidentally fall back on it.

I think there should be a simple way to have a primary or other index and keep it maintained but also allow it to be "disabled" for certain queries. Perhaps there could be an extra query param of "allow primary scan" that gets always set from things like cbq and the workbench since those are end-user tools, but would be off by default from any of the SDK's since those would be expected to follow our best practices for production operation.