[Feature] Add CVE categorization for etcd components

[shreyas-s-rao]

Feature (What you would like to be added):
Add CVE categorization for etcd components.

Motivation (Why is this needed?):
Allows us to define which CVEs are applicable for etcd components (druid, backup-restore, wrapper) in the context of gardener.

Approach/Hint to the implement solution (optional):
Add CVE categorization for:

• Add CVE categorization for etcd-druid #634
• Add CVE categorization for etcd-backup-restore etcd-backup-restore#644
• Add CVE categorization for etcd-wrapper etcd-wrapper#8

/area compliance security

[shreyas-s-rao]

Closing since all 3 PRs have been merged.
/close