Detect the amount of `CACHE` SQL queries

Following the discussion in:

• !31095 (comment 338858755)
• #216835 (closed)

I consider the CACHE SELECT * FROM to not be free, but rather be a memory-intensive operation.

The cached queries help with reducing DB load, but they still:

• consume memory
• require as to re-instantiate each AR object
• require as to re-instantiate each relation of the object
• makes us spend additional CPU-cycles to look into a list of cached queries.

We should treat the CACHE the same as N+1 queries. They are cheaper, but they are not cheap at all from ~memory perspective.

We need a way to detect the number of DB cached calls in the scope of the request and in the scope of the sidekiq worker.