[Fleet] show upgrade retries

[michel-laterman]

Part of the proposal for elastic/elastic-agent#778 would be to allow agents to retry certain actions (starting with the UPGRADE action).
In #139704 we suggest adding a new upgrade_status attribute to the agent documents in order to show when an agent is updating, or has completed its update.
When an agent is scheduled to retry an upgrade, the UI should reflect that state and show something like "retrying" instead of "updating", fleet-server will likely use the same upgrade_status attribute to show the upgrade state (instead of the top level agent status).

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)

[nimarezainia]

@michel-laterman @joshdover What would this signify to the user exactly? that we tried updating the agent but failed and now we are re-trying? i just want to make sure that we can prescribed what the user is to do if they see this status.

I agree that getting stuck in "Updating" state is not helpful and we need more context - but also want to find a way to help the operator to resolve.

[jlind23]

After discussing with @kpollich this will be moved to a later time.

[juliaElastic]

@kpollich Should we close this in favor of https://github.com/elastic/ingest-dev/issues/1621 ?

[kpollich]

Yep closing in favor of the private tracking issue