[1956257] Restricting os, flavor and workload labels and annotation to specific values

Description of problem:
The os, flavor and workload labels are copied to VMI template annotations and later to the VMI object, for every new VMI.

These labels are collected to our internal Telemetry, based on the kubevirt_vmi_phase_count metric, and must have a limited set of values, due to they way Prometheus work with labels.

Currently theses labels and annotation can be updated to any value, both in the template and the VMI object.

We should either enforce the specific labels and annotation to a specific allow list or update the metric collection to have this logic.

Version-Release number of selected component (if applicable):

How reproducible:
100%

Steps to Reproduce:
1. Update the os/ flavor/ workload annotations either in a running VMI or in a template or a YAML and create and run the VMI.
2. Check the value of kubevirt_vmi_phase_count
3.

Actual results:
kubevirt_vmi_phase_count os, flavor and workload labels will have any string that was set in the VM YAML/Template/VMI YAML used to configure the VMI.

Expected results:
kubevirt_vmi_phase_count should only include values from an allow list and the rest should have either 'none' for those that don't have these labels or 'custom' for users custom annotations.

Additional info: