core: bump rejected plans from debug -> info

As we have continued to see reports of #9506 we need to elevate this log
line as it is the only way to detect when plans are being *erroneously*
rejected.

Users who see this log line repeatedly should drain and restart the node
in the log line. This seems to workaorund the issue.

Please post any details on #9506!

.changelog/11416.txt

@@ -0,0 +1,3 @@
+```release-note:improvement
+core: Elevated rejected node plan log lines to help diagnose #9506
+```

nomad/plan_apply.go

@@ -477,7 +477,13 @@ func evaluatePlanPlacements(pool *EvaluatePool, snap *state.StateSnapshot, plan
 		if !fit {
 			// Log the reason why the node's allocations could not be made
 			if reason != "" {
-				logger.Debug("plan for node rejected", "node_id", nodeID, "reason", reason, "eval_id", plan.EvalID)
+				//TODO This was debug level and should return
+				//to debug level in the future. However until
+				//https://github.com/hashicorp/nomad/issues/9506
+				//is resolved this log line is the only way to
+				//monitor the disagreement between workers and
+				//the plan applier.
+				logger.Info("plan for node rejected", "node_id", nodeID, "reason", reason, "eval_id", plan.EvalID)
 			}
 			// Set that this is a partial commit
 			partialCommit = true