[DOCS] Improve connectors content

[lcawl]

Goals

• Make it easier to find all the connector configuration (reference) information at appropriate point of use
• Remove outdated or redundant information

Units of work

• Interim cleanup: Clarify method for creating connectors and how/when to use preconfigured settings per Alerts and Actions docs do not clearly state how to configure a connector (Kibana UI or preconfigured) #100268
  • Add tasks about creating and managing connectors from https://www.elastic.co/guide/en/kibana/current/action-types.html to a peer of the "Create and manage rules" page
• Add missing connector configuration details into the API reference pages [DOCS] Add configuration details to connector APIs  #133689
• Add missing prerequisites into the API reference pages [DOCS] Add prerequisites to responseOps APIs #133672
• Add missing connector configuration details into the UI
• Remove redundant details and screenshots from Connectors docs
• Merge content from https://www.elastic.co/guide/en/security/current/actions-api-overview.html then remove these duplicates: [DOCS] Deduplicate actions API reference #139763
• Link to appropriate third-party websites for setup details
• Split examples into detailed how-to pages e.g. [Actions][Docs] Modify connector documentation with the new MS Exchange online configuration requirements #112768 (comment)

[elasticmachine]

Pinging @elastic/response-ops (Team:ResponseOps)