Automatic merge from submit-queue (batch tested with PRs 58171, 58036, 60540). If you want to cherry-pick this change to another branch, please follow the instructions <a href="https://github.com/kubernetes/community/blob/master/contributors/devel/cherry-picks.md">here</a>.

Changing Flexvolume plugin directory on COS in GCE to a durable directory

**What this PR does / why we need it**: The original `/etc/srv/...` directory is in an overlayfs over a path in /tmp, so Flexvolume drivers are erased across node restarts for any reason. Changing it to non-tmpfs location.

Also removing redundant Flexvolume path injection in `config-test.sh` because it's already in `cluster/common.sh`.

**Which issue(s) this PR fixes** *(optional, in `fixes #<issue number>(, fixes #<issue_number>, ...)` format, will close the issue(s) when PR gets merged)*:
Fixes #57353

**Release note**:

```release-note
[action required] Default Flexvolume plugin directory for COS images on GCE is changed to `/home/kubernetes/flexvolume`.
```

/assign @roberthbailey @saad-ali 
/cc @chakri-nelluri @wongma7 
/sig storage