Improve filtering issues by label performance

closes #40500 (closed) and #37143 (closed)

Things to pay attention

A portion of code that filter labels by id got removed. I don't see a reason to have it
since we are skipping authorizations for projects and labels table is already joined in the query being filtered by name.

check: https://gitlab.com/gitlab-org/gitlab-ce/merge_requests/16136/diffs#e8d3aee82fd5a354fb303a289e50a5487a5e55ca_386_383

Before

All queries: before.pdf

After

All queries: after.pdf