[8.x] Optimize MlConfigVersion#getMinMaxMlConfigVersion (#125432) (#125500)

* Optimize MlConfigVersion#getMinMaxMlConfigVersion (#125432)

* Revert part of #125432

The logic is more complicated on 8.x than on main, so we need more of
the code to remain as it originally was.

Author: joegallo

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/MlConfigVersion.java

@@ -304,6 +304,9 @@ public static MlConfigVersion getMlConfigVersionForNode(DiscoveryNode node) {
         return fromId(node.getPre811VersionId().orElseThrow(() -> new IllegalStateException("getting legacy version id not possible")));
     }
 
+    // supports fromString below
+    private static final Pattern ML_VERSION_PATTERN = Pattern.compile("^(\\d+)\\.(\\d+)\\.(\\d+)(?:-\\w+)?$");
+
     // Parse an MlConfigVersion from a string.
     // Note that version "8.10.x" and "8.11.0" are silently converted to "10.0.0".
     // This is to support upgrade scenarios in pre-prod QA environments.
@@ -319,7 +322,7 @@ public static MlConfigVersion fromString(String str) {
         if (str.startsWith("8.10.") || str.equals("8.11.0")) {
             return V_10;
         }
-        Matcher matcher = Pattern.compile("^(\\d+)\\.(\\d+)\\.(\\d+)(?:-\\w+)?$").matcher(str);
+        Matcher matcher = ML_VERSION_PATTERN.matcher(str);
         if (matcher.matches() == false) {
             throw new IllegalArgumentException("ML config version [" + str + "] not valid");
         }

x-pack/plugin/core/src/main/java/org/elasticsearch/xpack/core/ml/action/GetTrainedModelsStatsAction.java

@@ -91,12 +91,6 @@ public static class TrainedModelStats implements ToXContentObject, Writeable {
             private final AssignmentStats deploymentStats;
             private final int pipelineCount;
 
-            private static final IngestStats EMPTY_INGEST_STATS = new IngestStats(
-                IngestStats.Stats.IDENTITY,
-                Collections.emptyList(),
-                Collections.emptyMap()
-            );
-
             public TrainedModelStats(
                 String modelId,
                 TrainedModelSizeStats modelSizeStats,
@@ -107,7 +101,7 @@ public TrainedModelStats(
             ) {
                 this.modelId = Objects.requireNonNull(modelId);
                 this.modelSizeStats = modelSizeStats;
-                this.ingestStats = ingestStats == null ? EMPTY_INGEST_STATS : ingestStats;
+                this.ingestStats = ingestStats == null ? IngestStats.IDENTITY : ingestStats;
                 if (pipelineCount < 0) {
                     throw new ElasticsearchException("[{}] must be a greater than or equal to 0", PIPELINE_COUNT.getPreferredName());
                 }