[1.24] cgmgr: create cgroups for systemd cgroup driver for dropped infra pods

[haircommander]

 The history here is a bit convoluted. Originally, runc created the cgroup for the infra container.
cAdvisor was built to assume the cgroup for the infra container would be created, and it uses
this to find the network metrics for the pod. When we dropped the infra container, cri-o needed to make this
cgroup so cAdvisor could still find the network metrics.

However, systemd didn't like the way we did it, and would remove the cgroup mid pod creation, which was fixed in
https://github.com/cri-o/cri-o/pull/6196. This actually caused the cgroup to not be created at all, which then caused
the networking metrics to not be gathered at all.

Thus, we do need to create a cgroup underneath the systemd cgroup. Attempt to use a slice for this, as systemd won't require a
process be underneath it.

What type of PR is this?

/kind bug

What this PR does / why we need it:

reverts #6196
fixes #6657

Which issue(s) this PR fixes:

Special notes for your reviewer:

partial cherry-pick of #6856, ignoring the last commit because it's not relevant for 1.24

Does this PR introduce a user-facing change?

Fix a bug where network metrics collection is broken with systemd cgroup driver and dropped infra containers.

[haircommander]

/hold

to allow testing against 1.25

[codecov]

Codecov Report

Merging #6949 (1edcf7f) into release-1.24 (b007cb6) will decrease coverage by 0.11%.
The diff coverage is 6.81%.

Additional details and impacted files

@@               Coverage Diff                @@
##           release-1.24    #6949      +/-   ##
================================================
- Coverage         42.89%   42.78%   -0.11%     
================================================
  Files               124      124              
  Lines             12749    12784      +35     
================================================
+ Hits               5469     5470       +1     
- Misses             6754     6788      +34     
  Partials            526      526              

[haircommander]

testing CI in #6969

[haircommander]

similar CI state as a README change, this is ready

@cri-o/cri-o-maintainers PTAL

/hold cancel

[sohankunkerkar]

/lgtm

[sohankunkerkar]

/lgtm

[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: haircommander, sohankunkerkar

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[openshift-ci]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: haircommander, sohankunkerkar

The full list of commands accepted by this bot can be found here.

The pull request process is described here

Needs approval from an approver in each of these files:

• OWNERS [haircommander]

Approvers can indicate their approval by writing /approve in a comment
Approvers can cancel approval by writing /approve cancel in a comment

[haircommander]

/cherry-pick release-1.23

[openshift-cherrypick-robot]

@haircommander: #6949 failed to apply on top of branch "release-1.23":

Applying: cgmgr: create cgroups for systemd cgroup driver for dropped infra pods
Using index info to reconstruct a base tree...
M	internal/config/cgmgr/cgmgr.go
M	test/cgroups.bats
Falling back to patching base and 3-way merge...
Auto-merging test/cgroups.bats
Auto-merging internal/config/cgmgr/cgmgr.go
CONFLICT (content): Merge conflict in internal/config/cgmgr/cgmgr.go
error: Failed to merge in the changes.
hint: Use 'git am --show-current-patch=diff' to see the failed patch
Patch failed at 0001 cgmgr: create cgroups for systemd cgroup driver for dropped infra pods
When you have resolved this problem, run "git am --continue".
If you prefer to skip this patch, run "git am --skip" instead.
To restore the original branch and stop patching, run "git am --abort".

In response to this:

/cherry-pick release-1.23

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