[API docs] Include alert suppression options in API docs for creating rules

[joepeeples]

Description

The API docs for creating rules need to include options for alert suppression, for the following rule types:

• Custom query — Added support for alert suppression in an earlier release, so we'll need to backport to 8.6.
• Threshold — Added support in 8.12.0, and we already have an open docs ticket for the overall feature:
  • [Detection Engine] Threshold rule alert suppression docs #4315

Background & resources

• PRs:
• Issues/metas:
• Point of contact: @vitaliidm, et al.
• Test environments:

Which documentation set does this change impact?

ESS and serverless

ESS release

8.12

Serverless release

Custom query rule already in prod. Threshold rule week of Jan 2, 2024?

Feature differences

Identical in ESS & serverless.

API docs impact

We need API docs!

Prerequisites, privileges, feature flags

Currently the threshold suppression feature is hidden behind the alertSuppressionForThresholdRuleEnabled flag.

Tasks

Preview Give feedback

1. Updates 8.12 and main — [Detection Engine] adds missing alert suppression API references #4479
2. Backports 8.11 thru 8.6 — Backport query rule alert suppression to API docs #4496