Make transport version ids have descending ordering

Transport version ids must be in descending order in definition files.
However, the compareTo for them was ascending and the validation used
reverse ordering. This commit fixes the compareTo so it uses desending
ordering and the validation uses natural ordering.

Author: rjernst

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/transport/TransportVersionId.java

@@ -22,7 +22,8 @@ static TransportVersionId fromString(String s) {
 
     @Override
     public int compareTo(TransportVersionId o) {
-        return Integer.compare(complete, o.complete);
+        // note: this is descending order so the arguments are reversed
+        return Integer.compare(o.complete, complete);
     }
 
     @Override

build-tools-internal/src/main/java/org/elasticsearch/gradle/internal/transport/ValidateTransportVersionResourcesTask.java

@@ -122,7 +122,7 @@ private void validateDefinition(TransportVersionDefinition definition, Set<Strin
         if (definition.ids().isEmpty()) {
             throwDefinitionFailure(definition, "does not contain any ids");
         }
-        if (Comparators.isInOrder(definition.ids(), Comparator.reverseOrder()) == false) {
+        if (Comparators.isInOrder(definition.ids(), Comparator.naturalOrder()) == false) {
             throwDefinitionFailure(definition, "does not have ordered ids");
         }
         for (int ndx = 0; ndx < definition.ids().size(); ++ndx) {