[Fleet] Enhance UI to have a quick-setup 'button' for on-prem deploys using --insecure option / self-signed certs

[EricDavisX]

Describe the feature:
Add some obvious UX element in the Fleet UI that would alert new self-managed users of the need to put:
ssl.verification_mode: none
... into the Fleet ES output settings. We could make this a hover link, or even a 'button' to do it for them (if that isn't too invasive). This is needed when user has self-signed certs (and the --insecure flag in Agent deploy). This area has generated many SDH and we can make this UX easier for users to start up with Fleet on self-managed deploys.

Describe a specific use case for the feature:
This is an extension of fixes put into elastic/beats#28007 wherein we have an opportunity to make the UX much better. Please review the issue to start.

The summary of where that landed is that we decided not make some behavior 'default' in Agent side based on the --insecure flag usage as we felt it was overstepping boundaries of what the user may want.

I submit we can offer a button on the kibana side, when we can detect the need to do the minimal additional setup in the Elasticsearch outputs section of Fleet to help users who will otherwise not know they need to do this unless they read the docs.

We could make it a one-time pop up button that is hidden based on some Kibana side value.

[elasticmachine]

Pinging @elastic/fleet (Team:Fleet)