[DOCS] Alerts tab added to cases

[nastasha-solomon]

Description

Dev issue: elastic/kibana#116501
Dev PR: elastic/kibana#130789

Cases now show two tabs: Activity and Alerts. From the Alerts tab users can view all of the alerts that are currently attached to the case. If no alerts are attached to the case, the following message displays on the Alerts tab.

Additional components of the new Alerts table that might need to be doc'd:

• Columns can be hidden, sorted alphabetically, and moved left or right (reordered).
  • The Columns option also lets users reorder columns.
  • The Sort fields option also allows users to choose one or more fields (columns) to sort in the table.
• Users can view alert details by clicking the View details button in the Actions column.
• Table display options can be modified, specifically (row?) density and row height.
• The Alerts table can be viewed in fullscreen mode.

alerts-tab.mp4

Notes

• Unsure how alerts are organized on the Alerts tab/table. What determines the order in which they're added to the table?
• This feature is in technical preview for 8.3. Might need to put it under the Technical preview section instead of the main case docs.
• Need more info on the "why" behind this feature. Is this to provide an expanded view of the alerts that are attached to a case so users can see main alert details at once? Does this allow users to view alerts that were added as a group (i.e. multiple alerts added to the case using the bulk add action).

[nastasha-solomon]

According to elastic/kibana#130789, the Alert tab is available in cases created in Security and Observability. It's not available for cases created in Stack Management. I verified this in the latest BC of 8.3.0 today.