When upgrading existing Policies in 7.9, Trusted Applications artifacts are not added

[kevinlog]

Kibana version:
7.10+

Elasticsearch version:
7.10+

Describe the bug:
When a user creates Endpoint Policies in 7.9 and upgrade, the Trusted Apps artifacts are not added to existing Policies. This causes newer Endpoints to send an Error in the Policy Response for User Artifacts.

If you view the Policies migrated from 7.9, you will see that the Trusted App policies do not contain the trustlist artifacts.

Note that newly created artifacts in 7.10+ will correctly add the trustlist artifacts.

Steps to reproduce:

1. Deploy 7.9 Kibana, create an Endpoint Policy
2. Upgrade to 7.10+, check existing Policy and see that trusted apps artifact isn't added
3. Try adding the Policy to a 7.10+ Endpoint and see a Policy response failure

Expected behavior:
Upgraded policies from 7.9 should get the Trusted Apps artifact added during migration

Screenshots (if relevant):

Any additional context:
A workaround for users would be to recreate Policies from 7.9, but this is a pain.

[paul-tavares]

I will take a look at this. The work around here might be to just add a trusted app entry - since that will trigger artifacts to be generated and manifest in the policies to be updated.