Version check is needed before injecting DevicePlugins feature gate

[Dagmawi Biru]

Charm: kubernetes-worker
Channel: 1.28/stable

Problem:
Newly deployed kubnernetes-worker unit/node is not starting up correctly, kubelet is crashing
with this error:

---
"command failed" err="failed to set feature gates from initial flags-based config: unrecognized feature gate: DevicePlugins"
snap.kubelet.daemon.service: Main process exited, code=exited, status=1/FAILURE
snap.kubelet.daemon.service: Failed with result 'exit-code'.
---

The cause for this appears to be the following

1. The "DevicePlugins" feature gate has been incorporated into k8s as of 1.28 as a generally available feature
https://github.com/kubernetes/kubernetes/pull/117656

2. However, the kubernetes-worker charm still inserts an invalid DevicePlugins gate in the kubelet config, which is leading to the kubelet daemon failing to start

3. This configuration is passed here
https://github.com/charmed-kubernetes/layer-kubernetes-common/blob/e329ebda02b38d94a0ef8eebc07c88b4bda79b9b/lib/charms/layer/kubernetes_common.py#L1172

The only check for this config to be added is for it to be a gpu enabled worker node. No check of the version is being made, hence the errors when trying to start kubelet on the node.

The charm needs to check that
----
A) The worker node has GPU enabled
B) The k8s version is at a version where the feature gate would be needed to be passed

[Chris Johnston (cjohnston)]

https://github.com/charmed-kubernetes/layer-kubernetes-common/pull/47