ILM "No custom node attributes configured" callout gives incorrect guidance if allocation was originally "Off"

[cjcenizal]

Note: This occurs on the 7.10 branch, not on master. Master exhibits a different bug: #81682.

To reproduce this bug, save a policy with allocation set to "Off". Edit the policy and select "Custom" instead. The callout below appears, informing that user that because there are no node attributes, node roles will be used instead:

Save the policy and go back and edit it again. Based on the callout, you'd expect allocation to be set to "Use cold nodes", but instead it's set to "Off". I think this is probably the desired behavior, in which case the solution will be to dynamically change the callout text depending on whether the policy is preconfigured with allocation set to "Default" or "Off".

[elasticmachine]

Pinging @elastic/es-ui (Team:Elasticsearch UI)

[jloleysens]

Do you think a simple fix in this case could be to just remove that last sentence from the copy "Cold nodes will be used instead"?

It seems reasonable to me that if you change a setting and receive a warning callout that setting has not changed. Otherwise we upgrade this to a danger callout and block if a user selects "Custom" with no node attrs, but that does not fit in with the underlying API.