Remove non-existent display_name field from the UserProfileUserInfo interface.

[azasypkin]

Summary

As of elastic/elasticsearch#84257, display_name is no longer returned from the Elasticsearch User Profiles API endpoints as it was decided that editable display_name isn't needed at the moment.

The synthetic display_name we render as a human readable user "identifier" follows this logic user.full_name (optional) || user.email (optional) || user.username (required). This PR exposes getUserDisplayName function that accepts UserProfile or User instances and returns the most suitable display name. Here is the context for this change shared by @MichaelMarcialis:

There was a concern about the consistency of display name values: it would appear odd to have some display names show as full name, some as email, and others as user name. Ultimately though, it was suggested that such situations would likely be edge cases, and we would proceed with the full name > email > user name cascade for display name.

It was also noted that Cloud users don’t really have a human-readable user name. They are assigned a random numeric ID on account creation, which wouldn’t look too pretty in user lists throughout Kibana. As such, it made sense to have email chosen for display name before user name, as email is required for Cloud accounts and would be far more identifiable than their user ID.

cc @jonathan-buttner

[elasticmachine]

Pinging @elastic/kibana-security (Team:Security)

[kc13greiner]

LGTM!

[kibana-ci]

💚 Build Succeeded

• Buildkite Build
• Commit: 200f27e
• Cloud Deployment

Metrics [docs]

Async chunks

Total size of all lazy-loaded chunks that will be downloaded as the user navigates the app

id	before	after	diff
security	513.4KB	513.5KB	+55.0B

Page load bundle

Size of the bundles that are downloaded on every page load. Target size is below 100kb

id	before	after	diff
security	51.9KB	52.0KB	+18.0B

Unknown metric groups

API count

id	before	after	diff
@kbn/user-profile-components	40	45	+5
security	240	245	+5
total			+10

History

• 💛 Build #66718 was flaky b37ee10
• 💚 Build #66364 succeeded 1d47401
• 💚 Build #66004 succeeded 97343d2

To update your PR or re-run it, just comment with:
@elasticmachine merge upstream

[kc13greiner]

LGTM!