Follow-up from "Copy and merge the existing Container Scanning docs to a new location"

The following discussion from !10649 (merged) should be addressed:

• @eread started a discussion: (+1 comment)

  Suggest deleting the use cases section and moving some of the content to the top.

  That way, I get the "why" first, then the "what" (the existing overview content), then the "how" (in the configuration sections).