[8.0] Add cgroup2 limit support

[sfayer]

Hi,

Here is an initial attempt at cgroup2 support via delegation... It supports MemoryLimitMB (int) and MemoryNoSwap (bool) options in ceParameters for both InProcessCE and SingularityCE (although I've not tested the latter). It's opportunistic, so should be transparent on sites that don't have cgroup delegation support (just running the payload unrestricted as before).

A hint for LHCb deployment: I suggest setting your limit a little shy of 4G, maybe around 3900 (as you won't get any benefit at sites with 4096 slots otherwise, as the pilot won't be protected without a small gap).

Closes #7853.

Regards,
Simon

BEGINRELEASENOTES
*WorkloadManagement
NEW: cgroup2 limit support
ENDRELEASENOTES

[sfayer]

Thanks for the review (I didn't notice it for a while, the notification must have got lost in the flurry of recent diracx activity :-)

I've added support for setting a CPU limit and written the requested documentation.

Regards,
Simon

[DIRACGridBot]

Sweep summary

Sweep ran in https://github.com/DIRACGrid/DIRAC/actions/runs/14472511501

Failed:

• integration
  cherry-pick 16a2dd1 into integration failed
  check merge conflicts on a local copy of this repository

  git fetch upstream
  git checkout upstream/integration -b cherry-pick-2-16a2dd1a3-integration
  git cherry-pick -x -m 1 16a2dd1a3
  # Fix the conflicts
  git cherry-pick --continue
  git commit --amend -m 'sweep: #8110 Add cgroup2 limit support' --author='Simon Fayer <sf105@ic.ac.uk>'
  git push -u origin cherry-pick-2-16a2dd1a3-integration
  
  # If you have the GitHub CLI installed the PR can be made with
  gh pr create \
       --label 'sweep:from rel-v8r0' \
       --base integration \
       --repo DIRACGrid/DIRAC \
       --title '[sweep:integration] Add cgroup2 limit support' \
       --body 'Sweep #8110 `Add cgroup2 limit support` to `integration`.
  
  Adding original author @sfayer as watcher.
  
  BEGINRELEASENOTES
  *WorkloadManagement
  NEW: cgroup2 limit support
  ENDRELEASENOTES
  Closes #8158'