Edit related_integrations field for custom rules in UI [classic]

[joepeeples]

Important

Do not merge to main until after 8.14.0 release, maybe until 8.15 feature freeze. This is to avoid adding 8.15 features into previous versions' branches (since those branches would be cut from main).

Contributes to #5099 by adding a step for Related integrations in the rule creation docs.

Preview

Create a detection rule

Twin PR for serverless

• https://github.com/elastic/staging-serverless-security-docs/pull/337

Related

• I'm expecting a conflict between this PR and Edit required_fields field for custom rules in UI [classic] #5287, since both PRs change the same lines in the same file. Will need to resolve by including both steps in the correct order that they appear in the UI (first Required fields, then Related integrations).

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[benironside]

Left a few small suggestions for your consideration, overall 🆒 🆒 🆒

[joepeeples]

This PR is ready to merge, but I don't think I should yet. If I merge now, then main will contain changes that won't be available in stateful until the 8.15 Stack release. Normally that's OK, since main always equals the next minor release. BUT if someone needs to update the same files with changes for 8.14 Stack release, they'll end up merging to main and then backporting to 8.14 and that's a problem, because the backport will bring this PR's 8.15 changes into the 8.14 branch.... I think? Or maybe not, if the backport is able to cherry-pick only the new changes intended for 8.14, not any and all diffs between main and 8.14...