Create new attribute for "Elastic Defend"

[joepeeples]

• Parent docs meta: [DOCS] [META] Rename integration to "Elastic Defend" security-docs#2463
• Related dev issue: https://github.com/elastic/security-team/issues/4759

Update the docs/shared/attributes.asciidoc file and create a new attribute elastic-defend with definition of Elastic Defend, which replaces the former endpoint-cloud-sec attribute (which was itself created to replace endpoint-sec in 8.3 via #2445). We are retaining the former attributes for use ONLY in versions prior to 8.5.