scheduler: add reconciler annotations to completed evals (#26188)

The output of the reconciler stage of scheduling is only visible via debug-level
logs, typically accessible only to the cluster admin. We can give job authors
better ability to understand what's happening to their jobs if we expose this
information to them in the `eval status` command.

Add the reconciler's desired updates to the evaluation struct so it can be
exposed in the API. This increases the size of evals by roughly 15% in the state
store, or a bit more when there are preemptions (but we expect this will be a
small minority of evals).

Ref: https://hashicorp.atlassian.net/browse/NMD-818
Fixes: https://github.com/hashicorp/nomad/issues/15564

api/evaluations.go

@@ -116,6 +116,7 @@ type Evaluation struct {
 	BlockedEval          string
 	RelatedEvals         []*EvaluationStub
 	FailedTGAllocs       map[string]*AllocationMetric
+	PlanAnnotations      *PlanAnnotations
 	ClassEligibility     map[string]bool
 	EscapedComputedClass bool
 	QuotaLimitReached    string