Show ILM phase in Index Management

[cjcenizal]

This feature was originally implemented but later removed because it was misusing the ES API (#45486). Per elastic/elasticsearch#46357:

Users hear "phase" and think about the stages in the Index Lifecycle Policy form, and reasonably form a mental model of an index moving from phase to phase -- but always being in a phase. Engineers hear "phase" and think of the actions a lifecycle policy takes upon an index entering a particular phase, actions which are of course finite. These two concepts are out of alignment.

...the long-term solution is to align the users' and engineers' perspectives. We need to let users view their indices in the UI in a way that aligns with their mental model.

This feature will be enabled by potentially breaking changes to the ES API that will represent phases (or stages) in a way that supports the mental model of an index moving from hot -> warm -> cold -> delete, and always being inside a phase/stage.

[elasticmachine]

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

[cjcenizal]

This should now be enabled by elastic/elasticsearch#51631