[extension/cgroupruntime] Add cgroup integration tests

[rogercoll]

Component(s)

extension/cgroupruntime

Is your feature request related to a problem? Please describe.

A new extension is being created to modify in runtime the values of GOMEMLIMIT and GOMAXPROCS based on the resource limits within a cgroup: #30289

The initial implementation includes the base files and unit tests needed for using the extension. However, to be part of the contrib distribution, integration tests also need to be added: #35472 (comment)

Describe the solution you'd like

Integration tests that modify cgroup resource limits and asserts the corresponding GOMEMLIMIT and GOMAXPROCS values.

Describe alternatives you've considered

No response

Additional context

No response

[rogercoll]

Component label will be available after #35472

[github-actions]

Pinging code owners for extension/cgroupruntime: @mx-psi @rogercoll. See Adding Labels via Comments if you do not have permissions to add labels yourself. For example, comment '/label priority:p2 -needs-triaged' to set the priority and remove the needs-triaged label.