Unmute and fix exponential_histogram.LoadFiltered CSV test (#137819)

Author: JonasKunz

muted-tests.yml

@@ -445,9 +445,6 @@ tests:
 - class: org.elasticsearch.xpack.inference.action.filter.ShardBulkInferenceActionFilterBasicLicenseIT
   method: testLicenseInvalidForInference {p0=false}
   issue: https://github.com/elastic/elasticsearch/issues/137691
-- class: org.elasticsearch.xpack.esql.qa.mixed.MixedClusterEsqlSpecIT
-  method: test {csv-spec:exponential_histogram.LoadFiltered}
-  issue: https://github.com/elastic/elasticsearch/issues/137727
 - class: org.elasticsearch.xpack.inference.InferenceRestIT
   method: test {p0=inference/70_text_similarity_rank_retriever/Text similarity reranker with min_score zero includes all docs}
   issue: https://github.com/elastic/elasticsearch/issues/137732

x-pack/plugin/esql/qa/testFixtures/src/main/resources/exponential_histogram.csv-spec

@@ -1,5 +1,5 @@
 loadFiltered
-required_capability: exponential_histogram
+required_capability: exponential_histogram_topn
 
 FROM exp_histo_sample | WHERE STARTS_WITH(instance, "dummy") | SORT instance | KEEP instance, responseTime
 ;

x-pack/plugin/esql/src/main/java/org/elasticsearch/xpack/esql/action/EsqlCapabilities.java

@@ -1547,6 +1547,11 @@ public enum Cap {
          */
         EXPONENTIAL_HISTOGRAM(EXPONENTIAL_HISTOGRAM_FEATURE_FLAG),
 
+        /**
+         * Support for exponential_histogram type in TOPN
+         */
+        EXPONENTIAL_HISTOGRAM_TOPN(EXPONENTIAL_HISTOGRAM_FEATURE_FLAG),
+
         /**
          * Create new block when filtering OrdinalBytesRefBlock
          */