[k8s] Define semantic conventions for k8s filesystem metrics

[ChrsMark]

Area(s)

area:k8s

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

As part of the K8s SemConv stability work we need to define k8s filesystem metrics that are already in use by the Opentelemetry Collector.

Related to #1032.

Describe the solution you'd like

The existing metrics in use that we need to define as semantic conventions are the following:

k8s.node.filesystem.available
k8s.node.filesystem.capacity
k8s.node.filesystem.usage
k8s.pod.filesystem.available
k8s.pod.filesystem.capacity
k8s.pod.filesystem.usage
container.filesystem.available
container.filesystem.capacity
container.filesystem.usage

Describe alternatives you've considered

No response

Additional context

No response