Currently when an ILM policy finishes its execution, the index moves into the `TerminalPolicyStep`,
denoted by a completed/completed/completed phase/action/step lifecycle execution state.
This commit changes the behavior so that the index lifecycle execution state halts at the last
configured phase's `PhaseCompleteStep`, so for instance, if an index were configured with a policy
containing a `hot` and `cold` phase, the index would stop at the `cold/complete/complete`
`PhaseCompleteStep`. This allows an ILM user to update the policy to add any later phases and have
indices configured to use that policy pick up execution at the newly added "later" phase. For
example, if a `delete` phase were added to the policy specified about, the index would then move
from `cold/complete/complete` into the `delete` phase.
Relates to #48431
deefc85d60