copy entity to user & hosts structs

[chennn1990]

Summary of your changes

Asset Inventory change:
create a nested hierarchy inside User & Host so the entity will be appeared also there instead of a sibling.

Related Issues

• Related:
  [Asset Discovery] Migrate to new nested *.entity.* schema #3554
  [Entity Store] Support *.entity.id fields on transform pivot kibana#233603

Checklist

• I have added tests that prove my fix is effective or that my feature works

[mergify]

This pull request does not have a backport label. Could you fix it @chennn1990? 🙏
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
• backport-active-all is the label that automatically backports to all active branches.
• backport-active-8 is the label that automatically backports to all active minor branches for the 8 major.
• backport-active-9 is the label that automatically backports to all active minor branches for the 9 major.