Add `related.entities` to asset inventory

[romulets]

Summary of your changes

• Rollback the previous changes of having asset renamed to entity, because there is no final decision of how should the field be named.
• Add related.entities field directly on inventory.go. I considered having another structure called Related that would the field entities. I didn't do it because I don't believe we should duplicate this data, Asset.Id is the source of truth, having a duplicated slice could lead to inconsistency, and even if we have a reference, seems like overcomplicating. I considered this related.entities as an ECS related concern. The asset.go map the domain used inside cloudbeat, and inventory.go is dealing with elasticsearch integration, ecs concern and so on. Of course we map the Asset to match ECS, we shouldn't have data translation layers here. But on this subject I decided to implement on inventory. I'm open to hear different opinions.

Screenshots

Related Issues

• Closes https://github.com/elastic/security-team/issues/10080

[mergify[bot]]

This pull request does not have a backport label. Could you fix it @romulets? 🙏 To fixup this pull request, you need to add the backport labels for the needed branches, such as:

• backport-v./d./d./d is the label to automatically backport to the 8./d branch. /d is the digit NOTE: backport-skip has been added to this pull request.

[github-actions[bot]]

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