making range aggregation untagged union (#2725)

* making range aggregation untagged union

* same as range query

* removed term range aggregation

* Revert "removed term range aggregation"

This reverts commit 1f832ef.

* rebase fix

(cherry picked from commit 231aa47)

Author: l-trotta

compiler/src/steps/validate-model.ts

@@ -597,7 +597,8 @@ export default async function validateModel (apiModel: model.Model, restSpec: Ma
 
       validateValueOf(valueOf, openGenerics)
     } else if (variants.kind === 'untagged') {
-      if (fqn(parentName) !== '_types.query_dsl:DecayFunction' &&
+      if (fqn(parentName) !== '_types.aggregations:AggregationRange' &&
+          fqn(parentName) !== '_types.query_dsl:DecayFunction' &&
           fqn(parentName) !== '_types.query_dsl:DistanceFeatureQuery' &&
           fqn(parentName) !== '_types.query_dsl:RangeQuery') {
         throw new Error(`Please contact the devtools team before adding new untagged variant ${fqn(parentName)}`)