Document new location fields for Cluster Image Scanning reports

What does this MR do and why?

Describe in detail what your merge request does and why.

This MR adds documentation for the new location fields which are being added to the security report schemas in order to support Cluster Image Scanning. These are being implemented in gitlab-org/security-products/security-report-schemas!83 (merged) and gitlab-org/security-products/analyzers/report!14 (merged).

As discussed in !69022 (comment 664125022), the location fingerprint will be composed of the agent_id/cluster_id, namespace, kubernetes resource name, kind, container, and the package `name.

MR acceptance checklist

This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.

• I have evaluated the MR acceptance checklist for this MR.