[Security][OpenAPI] Improve exceptions intro

[lcawl]

Summary

This PR copies information from https://www.elastic.co/guide/en/security/current/exceptions-api-overview.html into https://www.elastic.co/docs/api/doc/kibana/group/endpoint-security-exceptions-api

Based on https://github.com/elastic/kibana/blob/main/.buildkite/scripts/steps/code_generation/security_solution_codegen.sh, I generated the output for this change by running:

cd kibana/packages/kbn-securitysolution-exceptions-common
yarn openapi:bundle
cd kibana/oas_docs
make api-docs

Checklist

Check the PR satisfies following conditions.

Reviewers should verify this PR satisfies this list as well.

• Any text added follows EUI's writing guidelines, uses sentence case text and includes i18n support
• Documentation was added for features that require explanation or tutorials
• Unit or functional tests were updated or added to match the most common scenarios
• If a plugin configuration key changed, check if it needs to be allowlisted in the cloud and added to the docker list
• This was checked for breaking HTTP API changes, and any breaking changes have been approved by the breaking-change committee. The release_note:breaking label should be applied in these situations.
• Flaky Test Runner was used on any tests changed
• The PR description includes the appropriate Release Notes section, and the correct release_note:* label is applied per the guidelines

Identify risks

N/A

Preview

bump preview output/kibana.yaml:

[elasticmachine]

🤖 Jobs for this PR can be triggered through checkboxes. 🚧

ℹ️ To trigger the CI, please tick the checkbox below 👇

• Click to trigger kibana-pull-request for this PR!
• Click to trigger kibana-deploy-project-from-pr for this PR!

[lcawl]

Replaced by #202305