koordlet: fix can not collect psi metrics

[lucming]

Ⅰ. Describe what this PR does

koordlet can not collect psi metrics.

Ⅱ. Does this pull request fix one issue?

Ⅲ. Describe how to verify it

1. kernel with psi feature on

sudo grubby --update-kernel="/boot/vmlinuz-4.19.91-24.8.an8.x86_64" --args="psi=1 psi_v1=1"

update-kernel need to be replaced with the actual kernel version

2. open koordlet's feature for collecting psi metrics.

apiVersion: apps/v1
kind: DaemonSet
metadata:
  name: koordlet
spec:
  template:
    spec:
      containers:
        - name: koordlet
          image: registry.cn-beijing.aliyuncs.com/koordinator-sh/koordlet:v1.2.0
          command:
            - /koordlet
          args:
            - '-cgroup-root-dir=/host-cgroup/'
            - >-
              -feature-gates=BECPUEvict=true,BEMemoryEvict=true,CgroupReconcile=true,Accelerators=true,CPICollector=true,PSICollector=true
            - '-runtime-hooks-host-endpoint=/var/run/koordlet/koordlet.sock'
            - '--logtostderr=true'
            - '--v=4'

3. then we can see
   3.1. Access to koordlet's metrics api, but didn't get any info about psi
   3.2. check koordlet's log:
   
   It seems to be saying that there are no pressure related files under cpuacct cgroup
   3.3. looking at the cgroup, we can see that psi-related files exist
   

then there may be a problem with koordlet handling

The essential cause of the problem：
In golang, global variables are initialized before normal functions, so even though there is logic in the koordlet that modifies CgroupPathFormatter, the initialization of global variables only happens once and before the modification, so the logic in SupportedIfFileExistsInKubepods will use cgroupPathFormatterInSystemd, then the file related to psi can not be find, then making koordlet decide not support psi.

Ⅳ. Special notes for reviews

V. Checklist

• I have written necessary docs and comments
• I have added necessary unit tests and integration tests
• All checks passed in make test

[codecov]

Codecov Report

Patch coverage: 64.58% and project coverage change: +0.02 🎉

Comparison is base (382f7a0) 64.74% compared to head (6c5ebad) 64.76%.

Additional details and impacted files

@@            Coverage Diff             @@
##             main    #1402      +/-   ##
==========================================
+ Coverage   64.74%   64.76%   +0.02%     
==========================================
  Files         333      333              
  Lines       34296    34345      +49     
==========================================
+ Hits        22204    22243      +39     
- Misses      10458    10468      +10     
  Partials     1634     1634              

Flag	Coverage Δ
unittests	64.76% <64.58%> (+0.02%)	⬆️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
pkg/koordlet/util/system/cgroup_driver_linux.go	36.13% <64.10%> (+13.63%)	⬆️
pkg/koordlet/util/system/cgroup_driver.go	51.56% <66.66%> (+1.14%)	⬆️

... and 2 files with indirect coverage changes

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[saintube]

/lgtm
@lucming Please remember to mark the conversation as resolved.

[hormes]

/approve

[koordinator-bot]

[APPROVALNOTIFIER] This PR is APPROVED

This pull-request has been approved by: hormes

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