[k8s] Define semantic conventions for k8s pod resource (status, phase etc)

[ChrsMark]

Propose new conventions

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 pod resource phase/state related metrics that are already in use by the Opentelemetry Collector.

Related to https://github.com/open-telemetry/semantic-conventions/issues/1032

Describe the solution you'd like

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

k8s.pod.phase k8s.pod.status_reason

Could be similar to https://github.com/open-telemetry/semantic-conventions/pull/1784 and https://github.com/open-telemetry/semantic-conventions/pull/1668