[Documentation] Update documentation for QueryRecorder
Problem to solve
QueryRecorder is a tool used for detecting the N+1 queries problem from tests. This tool can be also used for detecting N+1 cached queries as well. We should update documentation, with examples and explanation of how to test N+1 cached queries.
Proposal
Update documentation for QueryRecorder, add examples on how to write tests for N+1 cached queries like we did for https://gitlab.com/gitlab-org/gitlab/-/blob/master/spec/lib/banzai/filter/label_reference_filter_spec.rb#L34-45
Edited by Nikola Milojevic