Throw an ISE rather than an hard assertion in SearchPhaseController#getTotalHits

This change turns an assertion into an IllegalStateException in SearchPhaseController#getTotalHits.
The goal is to help identify the cause of the failures in #37179
which seems to fail only in CI.
The assertion will be restored when the issue is solved (NORELEASE).

Author: jimczi

server/src/main/java/org/elasticsearch/action/search/SearchPhaseController.java

@@ -760,7 +760,13 @@ TotalHits getTotalHits() {
             if (trackTotalHitsUpTo == SearchContext.TRACK_TOTAL_HITS_DISABLED) {
                 return null;
             } else if (trackTotalHitsUpTo == SearchContext.TRACK_TOTAL_HITS_ACCURATE) {
-                assert totalHitsRelation == Relation.EQUAL_TO;
+                // NORELEASE The assertion below has been replaced by a runtime exception in order to debug
+                // https://github.com/elastic/elasticsearch/issues/37179.
+                // The assertion should be restored and the exception removed when this issue is solved.
+                // assert totalHitsRelation == Relation.EQUAL_TO;
+                if (totalHitsRelation != Relation.EQUAL_TO) {
+                    throw new IllegalStateException("Expected accurate total hits but got " + new TotalHits(totalHits, totalHitsRelation));
+                }
                 return new TotalHits(totalHits, totalHitsRelation);
             } else {
                 if (totalHits < trackTotalHitsUpTo) {