[Request] Add documentation for enable on install enhancement

[dplumlee]

Description

We merged the "enable on install" feature in 8.16 that allows users to enable prebuilt rules when they install them from the Rule Installation page. This includes per-field, bulk install, and through the rule flyout itself - all use cases are shown in screenshots in the UI. This specific feature is available via the UI and doesn't have any API differences.

Background & resources

• PRs: [Security Solution] Adds enable on install UI workflow to prebuilt rules page kibana#191529
• Point of contact: @dplumlee

Which documentation set does this change impact?

ESS and serverless

ESS release

8.16

Serverless release

This feature is already in serverless

Feature differences

The feature is identical between ESS and serverless

API docs impact

N/A

Prerequisites, privileges, feature flags

No response