What does this MR do?
This MR configure Gitlab::Redis to use a pool with a size related with the number of threads running the current process.
Are there points in the code the reviewer needs to double check?
Are there any race condition setting the pool class instance variable?
Why was this MR needed?
Screenshots (if relevant)
Does this MR meet the acceptance criteria?
CHANGELOG entry added
API support added
Added for this feature/bug
All builds are passing
Conform by the merge request performance guides
Conform by the style guides
Branch has no merge conflicts with
master(if you do - rebase it please)
Squashed related commits together
What are the relevant issue numbers?
Relates #18663 (moved)