[Alerting] [Docs] Improve alerting documents formatting and combine managing rules related docs.

[YulNaumenko]

Follow ups from the issue :

1. Improve the formatting of the jump pages (Stack rules and domain-specific pages).
2. Geo rule type looks odd under Domain-specific rules. Need to find the other way around this.
3. We might also look into combining Defining Rules/Managing Rules/Rule details.

[elasticmachine]

Pinging @elastic/kibana-alerting-services (Team:Alerting Services)

[ymao1]

@YulNaumenko Were there specific things to improve about the formatting of the jump pages?

[ymao1]

Based on a discussion with @gchaps, will be updating the docs in 3 separate PRs (for ease of review).

1. Move setup & prerequisites section into its own page [Alerting][Docs] Moving alerting setup to its own page #101323
2. Combining Defining Rules/Managing Rules/Rule details page into single Create and Manage Rules page [Alerting][Docs] Combine rule creation and management pages #101498
3. Combining Stack Rules/Domain-specific rules into single Rule types page [Alerting][Docs] Reformatting rule types docs #101420