Expand "Configure a lifecycle policy" docs

[kilfoyle]

This PR takes a chunk out of internal issue Requested fixes for data lifecycle docs that was initiated by a review of the ILM docs by our Support team.

It updates the "Configure a lifecycle policy" page to:

• Add Kibana steps where we currently show only the API steps.
  • In particular, when creating an index template users aren't always sure what to specify on the "Index settings" tab, so this adds an example config.
• Add a page overview
• Add a section about viewing the ILM status for an index or datastream
• Fix up smaller items, such as:
  • Explicitly call out the Kibana "Data retention" option.
  • Emphasize that lifecycle phase changes are based on time since rollover rather than index creation time
  • Warn about updating the logs@lifecycle and metrics@lifecycle policies since they affect a LOT of indices.
• Provide links for things like the index lifecycle actions, mappings, etc., to help people understand these options.

Please see preview pages:

• Configure a lifecycle policy
• Apply a lifecycle policy to an index
• View the lifecycle status of an index
• Update or switch a lifecycle policy

(For reference, here's the original version of the first page).

ES Data Management team, if any of you can please give this a technical review I'd be very grateful! 🙏 The API instructions aren't changed, with the exception that I added this section about calling the ILM explain API. The Kibana steps are all new.

[github-actions]

🔍 Preview links for changed docs:

• manage-data/data-store/data-streams/modify-data-stream.md
• manage-data/lifecycle/data-tiers.md
• manage-data/lifecycle/index-lifecycle-management/configure-lifecycle-policy.md
• manage-data/lifecycle/index-lifecycle-management/manage-existing-indices.md
• manage-data/lifecycle/index-lifecycle-management/policy-apply.md
• manage-data/lifecycle/index-lifecycle-management/policy-updates.md
• manage-data/lifecycle/index-lifecycle-management/policy-view-status.md

🔔 The preview site may take up to 3 minutes to finish building. These links will become live once it completes.

[samxbr]

Thanks for making this documentation change, I love the new Kibana steps! I just left a few comments.

[gmarouli]

@kilfoyle thank you for doing this, how nice to see it getting some love ❤️ .

I found some spots that might be misleading or incorrect, let me know if you want to go over through some of them offline as well, if that helps.

[kilfoyle]

@gmarouli and @samxbr Thanks so much for the careful review. 🙏

If you don't mind I'd love if you can take a second look. And do let me know if you don't think the new structure makes sense (I tried to explain the rationale in this comment).

• Configure a lifecycle policy
• Apply a lifecycle policy to an index
• View the lifecycle status of an index
• Update or switch a lifecycle policy

[kilfoyle]

Thanks a lot @yetanothertw for the excellent feedback!