Sidekiq not checking swap usage

[dvalfre]

Turns out that we configure the systemctl unit for Sidekiq to check MemoryMax. But processes got smarter and they use more swap, which systemctl is not monitoring.
To handle this, we want to expand the systemctl unit for Sidekiq to also set MemorySwapMax. Its value should be the same as that for MemoryMax.

[dvalfre]

We also want to explore the usage of MemoryHigh which set a soft limit for memory management that takes into account the whole virtual size of the process tree being monitored.