Data lifecycle docs: Rework the procedure; use UI rather than API

[kilfoyle]

More suggestions for Configure a lifecycle policy (see 29:00 to about 32:00)

• These steps differ from Manage time series data with data streams. The latter is correct/better: Create lifecycle policy, then create index template.

• Also, we shouldn't use the API for “Apply a policy to multiple indices”. Use the UI instead: Index management > select an index > Manage index > Remove lifecycle policy. And then assign a new (I think).

• In Configure a lifecycle policy, customers will update a lifecycle policy for one log file (e.g., I have K8s log index on the Hot phase and I want to keep it there, so I remove ILM policy from this specific log with this number). They expect the change to affect the next log file, but of course the next log reverts back to using the default lifecycle policy. [See 31:50: How to remove the policy for one specific index, then apply another policy.]

[kilfoyle]

This is completed via #1906

The UI steps have been added to Configure a lifecycle policy, and also some structure has been added to make the flow more clear.

Also, we now have steps for manually applying a policy, viewing the lifecycle status of an index,, and updating or switching a policy., so that should help people understand these procedures better.