Make kwctl aware of new severity and category annotations

[viccuad]

With the audit feature, we added support for new Policy Resource annotations (not to confuse with Policy metadata.yaml annotations), for policy severity and policy category. These are:

metadata:
  annotations:
    # one of critical, high, medium, low, info. Info is used when policy is in monitor mode
    # Empty by default, set by admin
    io.kubewarden.policy.severity: "high" 
    # freefrom string. Example: "PSP", "Sample", "Signing", "Other", "Compliance"
    # Empty by default, set by admin
    io.kubewarden.policy.category: "PSP"

Acceptance criteria

• Make these annotations work with kwctl annotate & kwctl inspect, so they are part of metadata.yaml as others.
• Make kwctl scaffold treat these, possibly setting empty values for them with an explanation comment.

[viccuad]

kwctl annotate already gobbles the annotations, and annotates the policy correctly. The annotations appear also in kwctl inspect.

The missing part then is kwctl scaffold, so they are added to the object metadata.annotations, if they are present.