[Monitoring] Open modal when user selects "Create default rules"

[estermv]

Summary

This issue is a follow up of #101565 to discuss the following feedback point from @katefarrar:

If a user click "Create default rules" from the "Alerts and rules" dropdown they don't receive any type of confirmation until there is a toast notification, which doesn't happen right away. Instead could the default rules modal pop up again and require them to select "Yes" so it's clear they have taken an action?

[elasticmachine]

Pinging @elastic/stack-monitoring (Team:Monitoring)

[elasticmachine]

Pinging @elastic/logs-metrics-ui (Team:logs-metrics-ui)

[ravikesarwani]

Do we know how long does it take to create the default rules?
I was thinking if bringing the modal again is really a good option or some kind of "processing" dialog is really a way to go.
In this case user really clicked on the menu to create the default rules and asking them again via a modal "do you really want to create the rules" doesn't seem like the best user experience.

[estermv]

I did some testing locally, the endpoint to create the default rules takes around 800ms.

We need to think also about how default rules are going to evolve on stack monitoring? I'm not sure if I remember correctly, but I think we talked or I read about allowing users to create each one of the default rules independently. If we want this, the dropdown will evolve to something more similar to what we have in other pages and the "Create default rules" won't exist.